2016
791.
M Manago, K Ishida, Z Mao, Y Maeno
Absence of the O 17 Knight-shift changes across the first-order phase transition line in Sr2RuO4 Journal Article
In: Physical Review B, vol. 94, no. 18, 2016.
@article{Manago2016b,
title = {Absence of the O 17 Knight-shift changes across the first-order phase transition line in Sr2RuO4},
author = {M Manago and K Ishida and Z Mao and Y Maeno},
doi = {10.1103/PhysRevB.94.180507},
year = {2016},
date = {2016-01-01},
journal = {Physical Review B},
volume = {94},
number = {18},
abstract = {We performed O17 nuclear magnetic resonance measurements on superconducting (SC) Sr2RuO4 under in-plane magnetic fields. We found that no new signal appears in the SC state and that the O17 Knight shifts obtained from the double-site measurements remain constant across the first-order phase-transition line, as well as across the second-order phase-transition line as already reported. The present results indicate that the SC spin susceptibility does not decrease in the high-field region, although a magnetization jump in the SC state was reported at low temperatures. Because the spin susceptibility is unchanged in the SC state in Sr2RuO4, we suggest that the first-order phase transition across the upper critical field should be interpreted as a depairing mechanism other than the conventional Pauli-paramagnetic effect. © 2016 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We performed O17 nuclear magnetic resonance measurements on superconducting (SC) Sr2RuO4 under in-plane magnetic fields. We found that no new signal appears in the SC state and that the O17 Knight shifts obtained from the double-site measurements remain constant across the first-order phase-transition line, as well as across the second-order phase-transition line as already reported. The present results indicate that the SC spin susceptibility does not decrease in the high-field region, although a magnetization jump in the SC state was reported at low temperatures. Because the spin susceptibility is unchanged in the SC state in Sr2RuO4, we suggest that the first-order phase transition across the upper critical field should be interpreted as a depairing mechanism other than the conventional Pauli-paramagnetic effect. © 2016 American Physical Society.
790.
B Chen, Z Deng, W Li, M Gao, Q Liu, C Z Gu, F X Hu, B G Shen, B Frandsen, S Cheung, L Lian, Y J Uemura, C Ding, S Guo, F Ning, T J S Munsie, M N Wilson, Y Cai, G Luke, Z Guguchia, S Yonezawa, Z Li, C Jin
New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping Journal Article
In: Scientific Reports, vol. 6, 2016, (cited By 12).
@article{Chen2016,
title = {New Fluoride-arsenide Diluted Magnetic Semiconductor (Ba,K)F(Zn,Mn)As with Independent Spin and Charge Doping},
author = {B Chen and Z Deng and W Li and M Gao and Q Liu and C Z Gu and F X Hu and B G Shen and B Frandsen and S Cheung and L Lian and Y J Uemura and C Ding and S Guo and F Ning and T J S Munsie and M N Wilson and Y Cai and G Luke and Z Guguchia and S Yonezawa and Z Li and C Jin},
doi = {10.1038/srep36578},
year = {2016},
date = {2016-01-01},
journal = {Scientific Reports},
volume = {6},
abstract = {We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the "1111" iron-based superconductors. The joint hole doping via (Ba,K) substitution &spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments. © 2016 The Author(s).},
note = {cited By 12},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report the discovery of a new fluoride-arsenide bulk diluted magnetic semiconductor (Ba,K)F(Zn,Mn)As with the tetragonal ZrCuSiAs-type structure which is identical to that of the "1111" iron-based superconductors. The joint hole doping via (Ba,K) substitution &spin doping via (Zn,Mn) substitution results in ferromagnetic order with Curie temperature up to 30 K and demonstrates that the ferromagnetic interactions between the localized spins are mediated by the carriers. Muon spin relaxation measurements confirm the intrinsic nature of the long range magnetic order in the entire volume in the ferromagnetic phase. This is the first time that a diluted magnetic semiconductor with decoupled spin and charge doping is achieved in a fluoride compound. Comparing to the isostructure oxide counterpart of LaOZnSb, the fluoride DMS (Ba,K)F(Zn,Mn)As shows much improved semiconductive behavior that would be benefit for further application developments. © 2016 The Author(s).
789.
D Jerome, S Yonezawa
Novel superconducting phenomena in quasi-one-dimensional Bechgaard salts Journal Article
In: Comptes Rendus Physique, vol. 17, no. 3-4, pp. 357-375, 2016, (cited By 9).
@article{Jerome2016357,
title = {Novel superconducting phenomena in quasi-one-dimensional Bechgaard salts},
author = {D Jerome and S Yonezawa},
doi = {10.1016/j.crhy.2015.12.003},
year = {2016},
date = {2016-01-01},
journal = {Comptes Rendus Physique},
volume = {17},
number = {3-4},
pages = {357-375},
abstract = {It is the saturation of the transition temperature Tc in the range of 24 K for known materials in the late sixties that triggered the search for additional materials offering new coupling mechanisms leading in turn to higher Tc's. As a result of this stimulation, superconductivity in organic matter was discovered in tetramethyl-tetraselenafulvalene-hexafluorophosphate, (TMTSF)2PF6, in 1979, in the laboratory founded at Orsay by Professor Friedel and his colleagues in 1962. Although this conductor is a prototype example for low-dimensional physics, we mostly focus in this article on the superconducting phase of the ambient-pressure superconductor (TMTSF)2ClO4, which has been studied most intensively among the TMTSF salts. We shall present a series of experimental results supporting nodal d-wave symmetry for the superconducting gap in these prototypical quasi-one-dimensional conductors. © 2015 Académie des sciences.},
note = {cited By 9},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
It is the saturation of the transition temperature Tc in the range of 24 K for known materials in the late sixties that triggered the search for additional materials offering new coupling mechanisms leading in turn to higher Tc's. As a result of this stimulation, superconductivity in organic matter was discovered in tetramethyl-tetraselenafulvalene-hexafluorophosphate, (TMTSF)2PF6, in 1979, in the laboratory founded at Orsay by Professor Friedel and his colleagues in 1962. Although this conductor is a prototype example for low-dimensional physics, we mostly focus in this article on the superconducting phase of the ambient-pressure superconductor (TMTSF)2ClO4, which has been studied most intensively among the TMTSF salts. We shall present a series of experimental results supporting nodal d-wave symmetry for the superconducting gap in these prototypical quasi-one-dimensional conductors. © 2015 Académie des sciences.
788.
S Kasahara, T Yamashita, A Shi, R Kobayashi, Y Shimoyama, T Watashige, K Ishida, T Terashima, T Wolf, F Hardy, C Meingast, H V Löhneysen, A Levchenko, T Shibauchi, Y Matsuda
Giant superconducting fluctuations in the compensated semimetal FeSe at the BCS-BEC crossover Journal Article
In: Nature Communications, vol. 7, 2016.
@article{Kasahara2016,
title = {Giant superconducting fluctuations in the compensated semimetal FeSe at the BCS-BEC crossover},
author = {S Kasahara and T Yamashita and A Shi and R Kobayashi and Y Shimoyama and T Watashige and K Ishida and T Terashima and T Wolf and F Hardy and C Meingast and H V Löhneysen and A Levchenko and T Shibauchi and Y Matsuda},
doi = {10.1038/ncomms12843},
year = {2016},
date = {2016-01-01},
journal = {Nature Communications},
volume = {7},
abstract = {The physics of the crossover between weak-coupling Bardeen-Cooper-Schrieffer (BCS) and strong-coupling Bose-Einstein condensate (BEC) limits gives a unified framework of quantum-bound (superfluid) states of interacting fermions. This crossover has been studied in the ultracold atomic systems, but is extremely difficult to be realized for electrons in solids. Recently, the superconducting semimetal FeSe with a transition temperature Tc =8.5 K has been found to be deep inside the BCS-BEC crossover regime. Here we report experimental signatures of preformed Cooper pairing in FeSe, whose energy scale is comparable to the Fermi energies. In stark contrast to usual superconductors, large non-linear diamagnetism by far exceeding the standard Gaussian superconducting fluctuations is observed below T∗∼20 K, providing thermodynamic evidence for prevailing phase fluctuations of superconductivity. Nuclear magnetic resonance and transport data give evidence of pseudogap formation at ∼T∗. The multiband superconductivity along with electron-hole compensation in FeSe may highlight a novel aspect of the BCS-BEC crossover physics. © The Author(s) 2016.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The physics of the crossover between weak-coupling Bardeen-Cooper-Schrieffer (BCS) and strong-coupling Bose-Einstein condensate (BEC) limits gives a unified framework of quantum-bound (superfluid) states of interacting fermions. This crossover has been studied in the ultracold atomic systems, but is extremely difficult to be realized for electrons in solids. Recently, the superconducting semimetal FeSe with a transition temperature Tc =8.5 K has been found to be deep inside the BCS-BEC crossover regime. Here we report experimental signatures of preformed Cooper pairing in FeSe, whose energy scale is comparable to the Fermi energies. In stark contrast to usual superconductors, large non-linear diamagnetism by far exceeding the standard Gaussian superconducting fluctuations is observed below T∗∼20 K, providing thermodynamic evidence for prevailing phase fluctuations of superconductivity. Nuclear magnetic resonance and transport data give evidence of pseudogap formation at ∼T∗. The multiband superconductivity along with electron-hole compensation in FeSe may highlight a novel aspect of the BCS-BEC crossover physics. © The Author(s) 2016.
2015
787.
N Kikugawa, R Baumbach, J S Brooks, T Terashima, S Uji, Y Maeno
Single-Crystal Growth of a Perovskite Ruthenate SrRuO3 by the Floating-Zone Method Journal Article
In: Crystal Growth and Design, vol. 15, no. 11, pp. 5573-5577, 2015.
@article{Kikugawa20155573,
title = {Single-Crystal Growth of a Perovskite Ruthenate SrRuO3 by the Floating-Zone Method},
author = {N Kikugawa and R Baumbach and J S Brooks and T Terashima and S Uji and Y Maeno},
doi = {10.1021/acs.cgd.5b01248},
year = {2015},
date = {2015-01-01},
journal = {Crystal Growth and Design},
volume = {15},
number = {11},
pages = {5573-5577},
abstract = {We report single-crystal growth of a perovskite ruthenate SrRuO3 by the floating-zone method using an infrared image furnace. By employing a cold trap for the growth, we prevented the evaporated RuO2 from coating the inner surface of a quartz tube and were thereby able to maintain a stable molten zone during the growth. Powder X-ray and Laue diffraction measurements confirmed the quality of the grown single crystal. The crystal was cut into a 1.4 mm × 1.4 mm × 3.0 mm rectangle that was characterized by magnetic susceptibility, magnetization, and specific heat measurements. The crystal showed a ferromagnetic transition with a Curie temperature of 163.5 K, and the coercive field was as low as 0.004 T. The residual resistivity was 1.05 cm, corresponding to a residual resistivity ratio of 192. These results indicate that the grown crystal is high-quality. Electrical resistivity measurements show temperature-squared behavior, revealing that a Fermi-liquid-like electron-electron scattering is dominant. Together with a large electronic specific heat coefficient with 30 mJ K-2 mol-1, we confirm that the ferromagnetic SrRuO3 is a strongly correlated material. © 2015 American Chemical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report single-crystal growth of a perovskite ruthenate SrRuO3 by the floating-zone method using an infrared image furnace. By employing a cold trap for the growth, we prevented the evaporated RuO2 from coating the inner surface of a quartz tube and were thereby able to maintain a stable molten zone during the growth. Powder X-ray and Laue diffraction measurements confirmed the quality of the grown single crystal. The crystal was cut into a 1.4 mm × 1.4 mm × 3.0 mm rectangle that was characterized by magnetic susceptibility, magnetization, and specific heat measurements. The crystal showed a ferromagnetic transition with a Curie temperature of 163.5 K, and the coercive field was as low as 0.004 T. The residual resistivity was 1.05 cm, corresponding to a residual resistivity ratio of 192. These results indicate that the grown crystal is high-quality. Electrical resistivity measurements show temperature-squared behavior, revealing that a Fermi-liquid-like electron-electron scattering is dominant. Together with a large electronic specific heat coefficient with 30 mJ K-2 mol-1, we confirm that the ferromagnetic SrRuO3 is a strongly correlated material. © 2015 American Chemical Society.
786.
K Ishida, M Manago, T Yamanaka, H Fukazawa, Z Q Mao, Y Maeno, K Miyake
Spin polarization enhanced by spin-triplet pairing in Sr2RuO4 probed by NMR Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 92, no. 10, 2015.
@article{Ishida2015,
title = {Spin polarization enhanced by spin-triplet pairing in Sr2RuO4 probed by NMR},
author = {K Ishida and M Manago and T Yamanaka and H Fukazawa and Z Q Mao and Y Maeno and K Miyake},
doi = {10.1103/PhysRevB.92.100502},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {92},
number = {10},
abstract = {We report a phenomenon intimately related to the spin-triplet superconductivity. It is well known that the spin susceptibility decreases below the superconducting transition temperature in almost all superconductors because of spin-singlet pair formation, while it may remain unchanged in a handful of spin-triplet exceptions. Here we report the observation in Sr2RuO4 with nuclear magnetic resonance that the spin susceptibility originating from the Ru-4d electron slightly increases by ∼2% of the total and becomes inhomogeneous in the superconducting state. These are reasonably explained if the electron pairs form the equal-spin pairing in the mixed state. A similar phenomenon was predicted for superfluid He340 years ago, but had never been demonstrated in any superconductor. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report a phenomenon intimately related to the spin-triplet superconductivity. It is well known that the spin susceptibility decreases below the superconducting transition temperature in almost all superconductors because of spin-singlet pair formation, while it may remain unchanged in a handful of spin-triplet exceptions. Here we report the observation in Sr2RuO4 with nuclear magnetic resonance that the spin susceptibility originating from the Ru-4d electron slightly increases by ∼2% of the total and becomes inhomogeneous in the superconducting state. These are reasonably explained if the electron pairs form the equal-spin pairing in the mixed state. A similar phenomenon was predicted for superfluid He340 years ago, but had never been demonstrated in any superconductor. © 2015 American Physical Society.
785.
K Saitoh, S Kashiwaya, H Kashiwaya, Y Mawatari, Y Asano, Y Tanaka, Y Maeno
Inversion symmetry of Josephson current as test of chiral domain wall motion in Sr2RuO4 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 92, no. 10, 2015.
@article{Saitoh2015,
title = {Inversion symmetry of Josephson current as test of chiral domain wall motion in Sr2RuO4},
author = {K Saitoh and S Kashiwaya and H Kashiwaya and Y Mawatari and Y Asano and Y Tanaka and Y Maeno},
doi = {10.1103/PhysRevB.92.100504},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {92},
number = {10},
abstract = {Clarifying the chiral domain structure of superconducting Sr2RuO4 has been a long-standing issue in identifying its peculiar topological superconducting state. We evaluated the critical current Ic versus the magnetic field H of Nb/Sr2RuO4 Josephson junctions, changing the junction dimension in expectation of that the number of domains in the junction is controlled. Ic(H) exhibits a recovery from inversion symmetry breaking to invariance when the dimension is reduced to several microns. This inversion invariant behavior indicates the disappearance of domain walls; thus, the size of a single domain is estimated at approximately several microns. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Clarifying the chiral domain structure of superconducting Sr2RuO4 has been a long-standing issue in identifying its peculiar topological superconducting state. We evaluated the critical current Ic versus the magnetic field H of Nb/Sr2RuO4 Josephson junctions, changing the junction dimension in expectation of that the number of domains in the junction is controlled. Ic(H) exhibits a recovery from inversion symmetry breaking to invariance when the dimension is reduced to several microns. This inversion invariant behavior indicates the disappearance of domain walls; thus, the size of a single domain is estimated at approximately several microns. © 2015 American Physical Society.
784.
S Yonezawa, T Higuchi, Y Sugimoto, C Sow, Y Maeno
Compact AC susceptometer for fast sample characterization down to 0.1 K Journal Article
In: Review of Scientific Instruments, vol. 86, no. 9, 2015.
@article{Yonezawa2015,
title = {Compact AC susceptometer for fast sample characterization down to 0.1 K},
author = {S Yonezawa and T Higuchi and Y Sugimoto and C Sow and Y Maeno},
doi = {10.1063/1.4929871},
year = {2015},
date = {2015-01-01},
journal = {Review of Scientific Instruments},
volume = {86},
number = {9},
abstract = {We report a new design of an AC magnetic susceptometer compatible with the Physical Properties Measurement System (PPMS) by Quantum Design, as well as with its adiabatic demagnetization refrigerator option. With the elaborate compact design, the susceptometer allows simple and quick sample mounting process. The high performance of the susceptometer down to 0.1 K is demonstrated using several superconducting and magnetic materials. This susceptometer provides a method to quickly investigate qualities of a large number of samples in the wide temperature range between 0.1 and 300 K. © 2015 AIP Publishing LLC.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report a new design of an AC magnetic susceptometer compatible with the Physical Properties Measurement System (PPMS) by Quantum Design, as well as with its adiabatic demagnetization refrigerator option. With the elaborate compact design, the susceptometer allows simple and quick sample mounting process. The high performance of the susceptometer down to 0.1 K is demonstrated using several superconducting and magnetic materials. This susceptometer provides a method to quickly investigate qualities of a large number of samples in the wide temperature range between 0.1 and 300 K. © 2015 AIP Publishing LLC.
783.
C W Hicks, A S Gibbs, L Zhao, P Kushwaha, H Borrmann, A P Mackenzie, H Takatsu, S Yonezawa, Y Maeno, E A Yelland
Quantum oscillations and magnetic reconstruction in the delafossite PdCrO2 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 92, no. 1, 2015.
@article{Hicks2015,
title = {Quantum oscillations and magnetic reconstruction in the delafossite PdCrO2},
author = {C W Hicks and A S Gibbs and L Zhao and P Kushwaha and H Borrmann and A P Mackenzie and H Takatsu and S Yonezawa and Y Maeno and E A Yelland},
doi = {10.1103/PhysRevB.92.014425},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {92},
number = {1},
abstract = {We report quantum oscillation data on the metallic triangular antiferromagnet PdCrO2. We find that, to very high accuracy, the observed frequencies of PdCrO2 can be reproduced by reconstruction of the (nonmagnetic) PdCoO2 Fermi surface into a reduced zone. The reduced zone corresponds to a magnetic cell containing six chromium sites, giving a 3×3 in-plane reconstruction, and ×2 interplane reconstruction. The interplane ordering represents a reduction in lattice symmetry, possibly to monoclinic, and an associated lattice distortion is expected. In addition, we report a magnetic transition under an applied in-plane field that is probably equivalent to the spin-flop transition reported for CuCrO2, and present data on its field-angle dependence. We also report measurements of the resistivity of PdCrO2 up to 500 K. © 2015 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report quantum oscillation data on the metallic triangular antiferromagnet PdCrO2. We find that, to very high accuracy, the observed frequencies of PdCrO2 can be reproduced by reconstruction of the (nonmagnetic) PdCoO2 Fermi surface into a reduced zone. The reduced zone corresponds to a magnetic cell containing six chromium sites, giving a 3×3 in-plane reconstruction, and ×2 interplane reconstruction. The interplane ordering represents a reduction in lattice symmetry, possibly to monoclinic, and an associated lattice distortion is expected. In addition, we report a magnetic transition under an applied in-plane field that is probably equivalent to the spin-flop transition reported for CuCrO2, and present data on its field-angle dependence. We also report measurements of the resistivity of PdCrO2 up to 500 K. © 2015 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
782.
D L Cortie, T Buck, M H Dehn, R F Kiefl, C D P Levy, R M L McFadden, G D Morris, M R Pearson, Z Salman, Y Maeno, W A MacFarlane
Spin fluctuations in the exotic metallic state of Sr2RuO4 studied with β-NMR Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 91, no. 24, 2015.
@article{Cortie2015,
title = {Spin fluctuations in the exotic metallic state of Sr2RuO4 studied with β-NMR},
author = {D L Cortie and T Buck and M H Dehn and R F Kiefl and C D P Levy and R M L McFadden and G D Morris and M R Pearson and Z Salman and Y Maeno and W A MacFarlane},
doi = {10.1103/PhysRevB.91.241113},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {91},
number = {24},
abstract = {A β-NMR study was performed on a Sr2RuO4 crystal in the metallic state using a beam of spin-polarized 8Li+ implanted at a mean depth of 90 nm. The 8Li+ spin-lattice relaxation rate is strongly influenced by the onset of incommensurate spin fluctuations. The nuclear relaxation rate can be explained using previously published bulk 17O NMR and inelastic neutron spectroscopy measurements of the dynamic magnetic susceptibility to model the hyperfine coupling. A well-resolved quadrupolar-split NMR for 8Li+ implies a static stopping position in an interstitial site. The 8Li+ Knight shift is highly sensitive to the anisotropic static susceptibility. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A β-NMR study was performed on a Sr2RuO4 crystal in the metallic state using a beam of spin-polarized 8Li+ implanted at a mean depth of 90 nm. The 8Li+ spin-lattice relaxation rate is strongly influenced by the onset of incommensurate spin fluctuations. The nuclear relaxation rate can be explained using previously published bulk 17O NMR and inelastic neutron spectroscopy measurements of the dynamic magnetic susceptibility to model the hyperfine coupling. A well-resolved quadrupolar-split NMR for 8Li+ implies a static stopping position in an interstitial site. The 8Li+ Knight shift is highly sensitive to the anisotropic static susceptibility. © 2015 American Physical Society.
781.
D Shibata, H Tanaka, S Yonezawa, T Nojima, Y Maeno
Quenched metastable vortex states in Sr2RuO4 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 91, no. 10, 2015.
@article{Shibata2015,
title = {Quenched metastable vortex states in Sr2RuO4},
author = {D Shibata and H Tanaka and S Yonezawa and T Nojima and Y Maeno},
doi = {10.1103/PhysRevB.91.104514},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {91},
number = {10},
abstract = {Sr2RuO4, a leading-candidate spin-triplet superconductor and a highly anisotropic quasi-two-dimensional type II superconductor, provides a unique opportunity to study unconventional as well as conventional vortex phases. To investigate its vortex-matter phases, we studied the ac susceptibility of Sr2RuO4 for fields parallel to the RuO2 plane by adapting two different thermal processes: In addition to the ordinary field sweep (FS) process, we employed the "each-point field-cooling" (EPFC) process, in which the superconductivity is once thermally destroyed before collecting the data. We find that the ac susceptibility signal substantially changes with the EPFC process. This result indicates that we succeed in inducing new metastable vortex states via the EPFC process. We also find a new field scale H∗1, below which the FS and EPFC processes provide the same value of the ac susceptibility. This new field scale suggests a liquidlike vortex state in the low-field region. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Sr2RuO4, a leading-candidate spin-triplet superconductor and a highly anisotropic quasi-two-dimensional type II superconductor, provides a unique opportunity to study unconventional as well as conventional vortex phases. To investigate its vortex-matter phases, we studied the ac susceptibility of Sr2RuO4 for fields parallel to the RuO2 plane by adapting two different thermal processes: In addition to the ordinary field sweep (FS) process, we employed the "each-point field-cooling" (EPFC) process, in which the superconductivity is once thermally destroyed before collecting the data. We find that the ac susceptibility signal substantially changes with the EPFC process. This result indicates that we succeed in inducing new metastable vortex states via the EPFC process. We also find a new field scale H∗1, below which the FS and EPFC processes provide the same value of the ac susceptibility. This new field scale suggests a liquidlike vortex state in the low-field region. © 2015 American Physical Society.
780.
S A Grigera, R A Borzi, D G Slobinsky, A S Gibbs, R Higashinaka, Y Maeno, T S Grigera
An intermediate state between the kagome-ice and the fully polarized state in Dy 2 Ti 2 O 7 Journal Article
In: Papers in Physics, vol. 7, 2015.
@article{Grigera2015,
title = {An intermediate state between the kagome-ice and the fully polarized state in Dy 2 Ti 2 O 7},
author = {S A Grigera and R A Borzi and D G Slobinsky and A S Gibbs and R Higashinaka and Y Maeno and T S Grigera},
doi = {10.4279/PIP.070009},
year = {2015},
date = {2015-01-01},
journal = {Papers in Physics},
volume = {7},
abstract = {Dy 2 Ti 2 O 7 is at present the cleanest example of a spin-ice material. Previous theoretical and experimental work on the first-order transition between the kagome-ice and the fully polarized state has been taken as a validation for the dipolar spin-ice model. Here we investigate in further depth this phase transition using ac-susceptibility and dc-magnetization, and compare this results with Monte-Carlo simulations and previous magnetization and specific heat measurements. We find signatures of an intermediate state between the kagome-ice and full polarization. This signatures are absent in current theoretical models used to describe spin-ice materials. © 2013, Instituto de Fisica de Liquidos y Sistemas Biologicos. All right reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Dy 2 Ti 2 O 7 is at present the cleanest example of a spin-ice material. Previous theoretical and experimental work on the first-order transition between the kagome-ice and the fully polarized state has been taken as a validation for the dipolar spin-ice model. Here we investigate in further depth this phase transition using ac-susceptibility and dc-magnetization, and compare this results with Monte-Carlo simulations and previous magnetization and specific heat measurements. We find signatures of an intermediate state between the kagome-ice and full polarization. This signatures are absent in current theoretical models used to describe spin-ice materials. © 2013, Instituto de Fisica de Liquidos y Sistemas Biologicos. All right reserved.
779.
B A Frandsen, S C Cheung, T Goko, L Liu, T Medina, T S J Munsie, G M Luke, P J Baker, M P Jimenez S., G Eguchi, S Yonezawa, Y Maeno, Y J Uemura
Superconducting properties of noncentrosymmetric superconductor CaIrSi3 investigated by muon spin relaxation and rotation Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 91, no. 1, 2015.
@article{Frandsen2015,
title = {Superconducting properties of noncentrosymmetric superconductor CaIrSi3 investigated by muon spin relaxation and rotation},
author = {B A Frandsen and S C Cheung and T Goko and L Liu and T Medina and T S J Munsie and G M Luke and P J Baker and M P Jimenez S. and G Eguchi and S Yonezawa and Y Maeno and Y J Uemura},
doi = {10.1103/PhysRevB.91.014511},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {91},
number = {1},
abstract = {We have employed muon spin relaxation and rotation (μSR) to investigate the superconducting properties of the noncentrosymmetric superconductor CaIrSi3. Measurements of single-crystal specimens confirm the development of a robust superconducting state below Tc=3.55±0.1K with a ground-state magnetic penetration depth of λL=288±10nm and a coherence length of ξ=28.8±0.1nm. The temperature evolution of the superfluid density indicates a nodeless superconducting gap structure dominated by an isotropic spin-singlet component in the dirty limit with a carrier density of n=(4.6±0.2)×1022cm-3 as determined by Hall resistance measurements. We find no evidence of spontaneous time-reversal symmetry breaking in the superconducting state within an accuracy of 0.05 G. These observations suggest that the influence of any spin-triplet pairing component or multiple gap structure associated with noncentrosymmetric physics is very weak or entirely absent in CaIrSi3. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We have employed muon spin relaxation and rotation (μSR) to investigate the superconducting properties of the noncentrosymmetric superconductor CaIrSi3. Measurements of single-crystal specimens confirm the development of a robust superconducting state below Tc=3.55±0.1K with a ground-state magnetic penetration depth of λL=288±10nm and a coherence length of ξ=28.8±0.1nm. The temperature evolution of the superfluid density indicates a nodeless superconducting gap structure dominated by an isotropic spin-singlet component in the dirty limit with a carrier density of n=(4.6±0.2)×1022cm-3 as determined by Hall resistance measurements. We find no evidence of spontaneous time-reversal symmetry breaking in the superconducting state within an accuracy of 0.05 G. These observations suggest that the influence of any spin-triplet pairing component or multiple gap structure associated with noncentrosymmetric physics is very weak or entirely absent in CaIrSi3. © 2015 American Physical Society.
778.
H Taniguchi, K Nishimura, S K Goh, S Yonezawa, Y Maeno
Higher-Tc superconducting phase in Sr2RuO4 induced by in-plane uniaxial pressure Journal Article
In: Journal of the Physical Society of Japan, vol. 84, no. 1, 2015.
@article{Taniguchi2015,
title = {Higher-Tc superconducting phase in Sr2RuO4 induced by in-plane uniaxial pressure},
author = {H Taniguchi and K Nishimura and S K Goh and S Yonezawa and Y Maeno},
doi = {10.7566/JPSJ.84.014707},
year = {2015},
date = {2015-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {84},
number = {1},
abstract = {We revealed that the superconducting transition temperature Tc of the multi-component superconductor Sr2RuO4 is enhanced to 3.3K under in-plane uniaxial pressure that reduces the tetragonal crystal symmetry. This result suggests that new superconducting phases with a one-component order parameter are induced. We have also clarified the in-plane pressure direction dependence of the emergence of this higher-Tc superconducting phase: pressure along the [100] direction is more favorable than pressure along the [110] direction. This result is probably closely related to the direct shortening of the in-plane Ru-O bond length along the pressure direction and the approach of the γ Fermi surface to the van Hove singularity under P||[100]. © 2015 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We revealed that the superconducting transition temperature Tc of the multi-component superconductor Sr2RuO4 is enhanced to 3.3K under in-plane uniaxial pressure that reduces the tetragonal crystal symmetry. This result suggests that new superconducting phases with a one-component order parameter are induced. We have also clarified the in-plane pressure direction dependence of the emergence of this higher-Tc superconducting phase: pressure along the [100] direction is more favorable than pressure along the [110] direction. This result is probably closely related to the direct shortening of the in-plane Ru-O bond length along the pressure direction and the approach of the γ Fermi surface to the van Hove singularity under P||[100]. © 2015 The Physical Society of Japan.
777.
Y Sugimoto, M S Anwar, S R Lee, Y J Shin, S Yonezawa, T W Noh, Y Maeno
Ferromagnetic Properties of SrRuO3 Thin Films Deposited on the Spin-Triplet Superconductor Sr2RuO4 Conference
vol. 75, 2015.
@conference{Sugimoto2015413,
title = {Ferromagnetic Properties of SrRuO3 Thin Films Deposited on the Spin-Triplet Superconductor Sr2RuO4},
author = {Y Sugimoto and M S Anwar and S R Lee and Y J Shin and S Yonezawa and T W Noh and Y Maeno},
doi = {10.1016/j.phpro.2015.12.050},
year = {2015},
date = {2015-01-01},
journal = {Physics Procedia},
volume = {75},
pages = {413-418},
abstract = {We report magnetic properties of epitaxial thin films of the itinerant ferromagnet SrRuO3 deposited on the cleaved ab surface of the spin-triplet superconductor Sr2RuO4. The films exhibit ferromagnetic transition near 160 K as in the bulk SrRuO3, although the films are under 1.7% compressive strain. The observed magnetization is even higher than that of the bulk SrRuO3. In addition, we newly found that the magnetization relaxation after field removal is strongly anisotropic: two relaxation processes are involved when magnetic domains are aligned along the ab-plane. © 2015 The Authors. Published by Elsevier B.V.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
We report magnetic properties of epitaxial thin films of the itinerant ferromagnet SrRuO3 deposited on the cleaved ab surface of the spin-triplet superconductor Sr2RuO4. The films exhibit ferromagnetic transition near 160 K as in the bulk SrRuO3, although the films are under 1.7% compressive strain. The observed magnetization is even higher than that of the bulk SrRuO3. In addition, we newly found that the magnetization relaxation after field removal is strongly anisotropic: two relaxation processes are involved when magnetic domains are aligned along the ab-plane. © 2015 The Authors. Published by Elsevier B.V.
776.
M S Anwar, Y Jae Shin, S Ran Lee, S Jin Kang, Y Sugimoto, S Yonezawa, T Won Noh, Y Maeno
In: Applied Physics Express, vol. 8, no. 1, 2015.
@article{Anwar2015,
title = {Erratum: Ferromagnetic SrRuO3 thin-film deposition on a spin-triplet superconductor Sr2RuO4 with a highly conducting interface (Appl. Phys. Express (2015) 8 (015502))},
author = {M S Anwar and Y Jae Shin and S Ran Lee and S Jin Kang and Y Sugimoto and S Yonezawa and T Won Noh and Y Maeno},
doi = {10.7567/APEX.8.019202},
year = {2015},
date = {2015-01-01},
journal = {Applied Physics Express},
volume = {8},
number = {1},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
775.
M S Anwar, Y Jae Shin, S Ran Lee, S Jin Kang, Y Sugimoto, S Yonezawa, T Won Noh, Y Maeno
Ferromagnetic SrRuO3 thin-film deposition on a spin-triplet superconductor Sr2RuO4 with a highly conducting interface Journal Article
In: Applied Physics Express, vol. 8, no. 1, 2015.
@article{Anwar2015b,
title = {Ferromagnetic SrRuO3 thin-film deposition on a spin-triplet superconductor Sr2RuO4 with a highly conducting interface},
author = {M S Anwar and Y Jae Shin and S Ran Lee and S Jin Kang and Y Sugimoto and S Yonezawa and T Won Noh and Y Maeno},
doi = {10.7567/APEX.8.015502},
year = {2015},
date = {2015-01-01},
journal = {Applied Physics Express},
volume = {8},
number = {1},
abstract = {Ferromagnetic SrRuO3 thin films are deposited on the ab surface of single crystals of the spin-triplet superconductor (TSC) Sr2RuO4 as substrates using pulsed laser deposition. The films are under a severe in-plane compressive strain. Nevertheless, the films exhibit ferromagnetic order with the easy axis along the c-direction below the Curie temperature of 158 K. The electrical transport reveals that the SrRuO3/Sr2RuO4 interface is highly conducting, in contrast with the interface between other normal metals and the ab surface of Sr2RuO4. Our results stimulate investigations on proximity effects between a ferromagnet and a TSC. © 2015 The Japan Society of Applied Physics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ferromagnetic SrRuO3 thin films are deposited on the ab surface of single crystals of the spin-triplet superconductor (TSC) Sr2RuO4 as substrates using pulsed laser deposition. The films are under a severe in-plane compressive strain. Nevertheless, the films exhibit ferromagnetic order with the easy axis along the c-direction below the Curie temperature of 158 K. The electrical transport reveals that the SrRuO3/Sr2RuO4 interface is highly conducting, in contrast with the interface between other normal metals and the ab surface of Sr2RuO4. Our results stimulate investigations on proximity effects between a ferromagnet and a TSC. © 2015 The Japan Society of Applied Physics.
774.
T Yamanaka, M Shimozawa, R Endo, Y Mizukami, H Shishido, T Terashima, T Shibauchi, Y Matsuda, K Ishida
Interface between heavy fermions and normal electrons investigated by spatially resolved nuclear magnetic resonance Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 92, no. 24, 2015.
@article{Yamanaka2015,
title = {Interface between heavy fermions and normal electrons investigated by spatially resolved nuclear magnetic resonance},
author = {T Yamanaka and M Shimozawa and R Endo and Y Mizukami and H Shishido and T Terashima and T Shibauchi and Y Matsuda and K Ishida},
doi = {10.1103/PhysRevB.92.241105},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {92},
number = {24},
abstract = {We have studied the superlattices with alternating block layers (BLs) of heavy-fermion superconductor CeCoIn5 and conventional-metal YbCoIn5 by site-selective nuclear magnetic resonance spectroscopy, which uniquely offers spatially resolved dynamical magnetic information. We find that the presence of antiferromagnetic fluctuations is confined to the Ce BLs, indicating that magnetic degrees of freedom of felectrons are quenched inside the Yb BLs. Contrary to simple expectations that the two dimensionalization enhances fluctuations, we observe that antiferromagnetic fluctuations are rapidly suppressed with decreasing Ce BL thickness. Moreover, the suppression is more prominent near the interfaces between the BLs. These results imply significant effects of local inversion symmetry breaking at the interfaces. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We have studied the superlattices with alternating block layers (BLs) of heavy-fermion superconductor CeCoIn5 and conventional-metal YbCoIn5 by site-selective nuclear magnetic resonance spectroscopy, which uniquely offers spatially resolved dynamical magnetic information. We find that the presence of antiferromagnetic fluctuations is confined to the Ce BLs, indicating that magnetic degrees of freedom of felectrons are quenched inside the Yb BLs. Contrary to simple expectations that the two dimensionalization enhances fluctuations, we observe that antiferromagnetic fluctuations are rapidly suppressed with decreasing Ce BL thickness. Moreover, the suppression is more prominent near the interfaces between the BLs. These results imply significant effects of local inversion symmetry breaking at the interfaces. © 2015 American Physical Society.
773.
M Manago, K Ishida, T D Matsuda, Y Onuki
Effect of Geomagnetism on 101Ru Nuclear Quadrupole Resonance Measurements of CeRu2 Journal Article
In: Journal of the Physical Society of Japan, vol. 84, no. 11, 2015.
@article{Manago2015,
title = {Effect of Geomagnetism on 101Ru Nuclear Quadrupole Resonance Measurements of CeRu2},
author = {M Manago and K Ishida and T D Matsuda and Y Onuki},
doi = {10.7566/JPSJ.84.115001},
year = {2015},
date = {2015-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {84},
number = {11},
abstract = {We performed 101Ru nuclear quadrupole resonance (NQR) measurements on the s-wave superconductor CeRu2 and found oscillatory behavior in the spin-echo amplitude at the |±1/2 虠 |±3/2 transitions but not at the |±3/2 虠 |±5/2 transitions. The modulation disappears in the superconducting state or in a magnetic shield, which implies a geomagnetic field effect. Our results indicate that the NQR spin-echo decay curve at the |±1/2 虠 |±3/2 transitions is sensitive to a weak magnetic field. © 2015 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We performed 101Ru nuclear quadrupole resonance (NQR) measurements on the s-wave superconductor CeRu2 and found oscillatory behavior in the spin-echo amplitude at the |±1/2 虠 |±3/2 transitions but not at the |±3/2 虠 |±5/2 transitions. The modulation disappears in the superconducting state or in a magnetic shield, which implies a geomagnetic field effect. Our results indicate that the NQR spin-echo decay curve at the |±1/2 虠 |±3/2 transitions is sensitive to a weak magnetic field. © 2015 The Physical Society of Japan.
772.
S Kitagawa, T Sekiya, S Araki, T C Kobayashi, K Ishida, T Kambe, T Kimura, N Nishimoto, K Kudo, M Nohara
Suppression of nonmagnetic insulating state by application of pressure in mineral tetrahedrite Cu12Sb4S13 Journal Article
In: Journal of the Physical Society of Japan, vol. 84, no. 9, 2015.
@article{Kitagawa2015,
title = {Suppression of nonmagnetic insulating state by application of pressure in mineral tetrahedrite Cu12Sb4S13},
author = {S Kitagawa and T Sekiya and S Araki and T C Kobayashi and K Ishida and T Kambe and T Kimura and N Nishimoto and K Kudo and M Nohara},
doi = {10.7566/JPSJ.84.093701},
year = {2015},
date = {2015-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {84},
number = {9},
abstract = {The mineral tetrahedrite Cu12Sb4S13 exhibits a first-order metal-insulator transition (MIT) at TMI = 85K and ambient pressure. We measured the 63Cu-NMR at ambient pressure and the resistivity and magnetic susceptibility at high pressures. 63Cu-NMR results indicate a nonmagnetic insulating ground state in this compound. The MIT is monotonically suppressed by pressure and disappears at ~1.0 GPa. Two other anomalies are observed in the resistivity measurements, and the pressure-temperature phase diagram of Cu12Sb4S13 is constructed. ©2015 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The mineral tetrahedrite Cu12Sb4S13 exhibits a first-order metal-insulator transition (MIT) at TMI = 85K and ambient pressure. We measured the 63Cu-NMR at ambient pressure and the resistivity and magnetic susceptibility at high pressures. 63Cu-NMR results indicate a nonmagnetic insulating ground state in this compound. The MIT is monotonically suppressed by pressure and disappears at ~1.0 GPa. Two other anomalies are observed in the resistivity measurements, and the pressure-temperature phase diagram of Cu12Sb4S13 is constructed. ©2015 The Physical Society of Japan.
771.
T Iye, M -H Julien, H Mayaffre, M Horvatić, C Berthier, K Ishida, H Ikeda, S Kasahara, T Shibauchi, Y Matsuda
Emergence of orbital nematicity in the tetragonal phase of BaFe2(As1-xPx)2 Journal Article
In: Journal of the Physical Society of Japan, vol. 84, no. 4, 2015.
@article{Iye2015,
title = {Emergence of orbital nematicity in the tetragonal phase of BaFe2(As1-xPx)2},
author = {T Iye and M -H Julien and H Mayaffre and M Horvatić and C Berthier and K Ishida and H Ikeda and S Kasahara and T Shibauchi and Y Matsuda},
doi = {10.7566/JPSJ.84.043705},
year = {2015},
date = {2015-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {84},
number = {4},
abstract = {We report on 75As-NMR measurements in single crystalline BaFe2(As0.96P0.04)2 for magnetic fields parallel to the orthorhombic [110]o and [100]o directions above the structural transition temperature TS ≃ 121 K. A large difference in the linewidth between the two field directions reveals in-plane anisotropy of the electric field gradient, even in the tetragonal phase. This provides microscopic evidence of population imbalance between As-4px and 4py orbitals, which reaches |nx - ny| /|nx + ny| ∼ 15% at T → TS and is a natural consequence of the orbital ordering of Fe-3dxz and dyz electrons. Surprisingly, this orbital polarization is found to be already static near room temperature, suggesting that it arises from the pinning of anisotropic orbital fluctuations by disorder. The effect is found to be stronger below ∼160 K, which coincides with the appearance of nematicity in previous torque and photoemission measurements. These results impose strong constraints on microscopic models of the nematic state. ©2015 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report on 75As-NMR measurements in single crystalline BaFe2(As0.96P0.04)2 for magnetic fields parallel to the orthorhombic [110]o and [100]o directions above the structural transition temperature TS ≃ 121 K. A large difference in the linewidth between the two field directions reveals in-plane anisotropy of the electric field gradient, even in the tetragonal phase. This provides microscopic evidence of population imbalance between As-4px and 4py orbitals, which reaches |nx - ny| /|nx + ny| ∼ 15% at T → TS and is a natural consequence of the orbital ordering of Fe-3dxz and dyz electrons. Surprisingly, this orbital polarization is found to be already static near room temperature, suggesting that it arises from the pinning of anisotropic orbital fluctuations by disorder. The effect is found to be stronger below ∼160 K, which coincides with the appearance of nematicity in previous torque and photoemission measurements. These results impose strong constraints on microscopic models of the nematic state. ©2015 The Physical Society of Japan.
770.
K Karube, T Hattori, K Ishida, N Kimura
In: Physical Review B - Condensed Matter and Materials Physics, vol. 91, no. 7, 2015.
@article{Karube2015,
title = {Ferromagnetic critical behavior in U(Co1-xFex)Al (0≤x≤0.02) studied by Co 59 nuclear quadrupole resonance measurements FERROMAGNETIC CRITICAL BEHAVIOR in U(Co ... K. KARUBE, T. HATTORI, K. ISHIDA, and N. KIMURA},
author = {K Karube and T Hattori and K Ishida and N Kimura},
doi = {10.1103/PhysRevB.91.075131},
year = {2015},
date = {2015-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {91},
number = {7},
abstract = {In order to investigate physical properties around a ferromagnetic (FM) quantum transition point and a tricritical point (TCP) in the itinerant-electron metamagnetic compound UCoAl, we have performed the Co59 nuclear quadrupole resonance (NQR) measurement for the Fe-substituted U(Co1-xFex)Al(x=0,0.5,1,and2%) in zero external magnetic field. The Fe concentration dependence of Co59-NQR spectra at low temperatures indicates that the first-order FM transition occurs at least above x=1%. The magnetic fluctuations along the c axis detected by the nuclear spin-spin relaxation rate 1/T2 exhibit an anomaly at Tmax∼20K and enhance with increasing x. These results are in good agreement with theoretical predictions and indicate the presence of prominent critical fluctuations at the TCP in this system. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In order to investigate physical properties around a ferromagnetic (FM) quantum transition point and a tricritical point (TCP) in the itinerant-electron metamagnetic compound UCoAl, we have performed the Co59 nuclear quadrupole resonance (NQR) measurement for the Fe-substituted U(Co1-xFex)Al(x=0,0.5,1,and2%) in zero external magnetic field. The Fe concentration dependence of Co59-NQR spectra at low temperatures indicates that the first-order FM transition occurs at least above x=1%. The magnetic fluctuations along the c axis detected by the nuclear spin-spin relaxation rate 1/T2 exhibit an anomaly at Tmax∼20K and enhance with increasing x. These results are in good agreement with theoretical predictions and indicate the presence of prominent critical fluctuations at the TCP in this system. © 2015 American Physical Society.
769.
A E Böhmer, T Arai, F Hardy, T Hattori, T Iye, T Wolf, H V Löhneysen, K Ishida, C Meingast
Origin of the tetragonal-to-orthorhombic phase transition in FeSe: A combined thermodynamic and NMR study of nematicity Journal Article
In: Physical Review Letters, vol. 114, no. 2, 2015.
@article{Böhmer2015,
title = {Origin of the tetragonal-to-orthorhombic phase transition in FeSe: A combined thermodynamic and NMR study of nematicity},
author = {A E Böhmer and T Arai and F Hardy and T Hattori and T Iye and T Wolf and H V Löhneysen and K Ishida and C Meingast},
doi = {10.1103/PhysRevLett.114.027001},
year = {2015},
date = {2015-01-01},
journal = {Physical Review Letters},
volume = {114},
number = {2},
abstract = {The nature of the tetragonal-to-orthorhombic structural transition at Ts≈90K in single crystalline FeSe is studied using shear-modulus, heat-capacity, magnetization, and nuclear magnetic resonance measurements. The transition is shown to be accompanied by a large shear-modulus softening, which is practically identical to that of underdoped Ba(Fe,Co)2As2, suggesting a very similar strength of the electron-lattice coupling. On the other hand, a spin-fluctuation contribution to the spin-lattice relaxation rate is only observed below Ts. This indicates that the structural, or "nematic," phase transition in FeSe is not driven by magnetic fluctuations. © 2015 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The nature of the tetragonal-to-orthorhombic structural transition at Ts≈90K in single crystalline FeSe is studied using shear-modulus, heat-capacity, magnetization, and nuclear magnetic resonance measurements. The transition is shown to be accompanied by a large shear-modulus softening, which is practically identical to that of underdoped Ba(Fe,Co)2As2, suggesting a very similar strength of the electron-lattice coupling. On the other hand, a spin-fluctuation contribution to the spin-lattice relaxation rate is only observed below Ts. This indicates that the structural, or "nematic," phase transition in FeSe is not driven by magnetic fluctuations. © 2015 American Physical Society.
2014
768.
S Kittaka, A Kasahara, T Sakakibara, D Shibata, S Yonezawa, Y Maeno, K Tenya, K Machida
Sharp magnetization jump at the first-order superconducting transition in Sr2 RuO4 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 90, no. 22, 2014.
@article{Kittaka2014,
title = {Sharp magnetization jump at the first-order superconducting transition in Sr2 RuO4},
author = {S Kittaka and A Kasahara and T Sakakibara and D Shibata and S Yonezawa and Y Maeno and K Tenya and K Machida},
doi = {10.1103/PhysRevB.90.220502},
year = {2014},
date = {2014-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {90},
number = {22},
abstract = {The magnetization and magnetic torque of a high-quality single crystal of Sr2RuO4 have been measured down to 0.1 K under precise control of the magnetic-field orientation. When the magnetic field is applied exactly parallel to the ab plane, a sharp magnetization jump 4πδM of (0.74±0.15) G at the upper critical field Hc2,ab∼15 kOe with a field hysteresis of 100 Oe is observed at low temperatures, evidencing a first-order superconducting-normal transition. A strong magnetic torque appearing when H is slightly tilted away from the ab plane confirms an intrinsic anisotropy Γ=ξa/ξc of as large as 60 even at 100 mK, in contrast with the observed Hc2 anisotropy of ∼20. The present results raise fundamental issues in both the existing spin-triplet and spin-singlet scenarios, providing, in turn, crucial hints toward the resolution of the superconducting nature of Sr2RuO4. © 2014 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The magnetization and magnetic torque of a high-quality single crystal of Sr2RuO4 have been measured down to 0.1 K under precise control of the magnetic-field orientation. When the magnetic field is applied exactly parallel to the ab plane, a sharp magnetization jump 4πδM of (0.74±0.15) G at the upper critical field Hc2,ab∼15 kOe with a field hysteresis of 100 Oe is observed at low temperatures, evidencing a first-order superconducting-normal transition. A strong magnetic torque appearing when H is slightly tilted away from the ab plane confirms an intrinsic anisotropy Γ=ξa/ξc of as large as 60 even at 100 mK, in contrast with the observed Hc2 anisotropy of ∼20. The present results raise fundamental issues in both the existing spin-triplet and spin-singlet scenarios, providing, in turn, crucial hints toward the resolution of the superconducting nature of Sr2RuO4. © 2014 American Physical Society.
767.
S Tsuchiya, M Matsuno, R Ishiguro, H Kashiwaya, S Kashiwaya, S Nomura, H Takayanagi, Y Maeno
Magnetization of a mesoscopic superconducting Sr2RuO4plate on Micro-dc-SQUIDs Journal Article
In: Journal of the Physical Society of Japan, vol. 83, no. 9, 2014.
@article{Tsuchiya2014,
title = {Magnetization of a mesoscopic superconducting Sr2RuO4plate on Micro-dc-SQUIDs},
author = {S Tsuchiya and M Matsuno and R Ishiguro and H Kashiwaya and S Kashiwaya and S Nomura and H Takayanagi and Y Maeno},
doi = {10.7566/JPSJ.83.094715},
year = {2014},
date = {2014-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {83},
number = {9},
abstract = {We report on the measurement of the magnetization of mesoscopic plates made of the chiral p-wave superconductor Sr2RuO4by using micro-dc-superconducting quantum interference devices (SQUIDs) positioned immediately below the plates. The high sensitivity of the micro-dc-SQUIDs is expected to enable the detection of direction of the chirality. We measured the magnetization of mesoscopic Sr2RuO4plate-like crystals and found residual magnetization at the zero external field in the thin sample and detected a first critical field Hc1symmetric against the magnetic field direction. The observed symmetric first critical field Hc1is consistent with the formation of multi-chiral domain structures. We carefully discuss the origin of the residual magnetization and conclude that it is due to the remnant vortices rather than the chiral edge current. © 2014 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report on the measurement of the magnetization of mesoscopic plates made of the chiral p-wave superconductor Sr2RuO4by using micro-dc-superconducting quantum interference devices (SQUIDs) positioned immediately below the plates. The high sensitivity of the micro-dc-SQUIDs is expected to enable the detection of direction of the chirality. We measured the magnetization of mesoscopic Sr2RuO4plate-like crystals and found residual magnetization at the zero external field in the thin sample and detected a first critical field Hc1symmetric against the magnetic field direction. The observed symmetric first critical field Hc1is consistent with the formation of multi-chiral domain structures. We carefully discuss the origin of the residual magnetization and conclude that it is due to the remnant vortices rather than the chiral edge current. © 2014 The Physical Society of Japan.
766.
S Yonezawa, T Kajikawa, Y Maeno
Specific-heat evidence of the first-order superconducting transition in Sr2RuO4 Journal Article
In: Journal of the Physical Society of Japan, vol. 83, no. 8, 2014.
@article{Yonezawa2014,
title = {Specific-heat evidence of the first-order superconducting transition in Sr2RuO4},
author = {S Yonezawa and T Kajikawa and Y Maeno},
doi = {10.7566/JPSJ.83.083706},
year = {2014},
date = {2014-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {83},
number = {8},
abstract = {We investigate the specific heat of ultra pure single crystals of Sr2RuO4, a leading candidate spin-triplet superconductor. For the fi rst time, we obtained specific-heat evidence of the first-order superconducting transition below 0.8 K, namely, divergent-like peaks and clear hysteresis in the specific heat at the upper critical field. The first-order occurs for all in-plane field directions. The specific-heat features for the first-order transition are found to be sensitive to sample quality; in particular, the hysteresis totally disappears in a sample with slightly lower quality. These thermodynamic observations provide crucial bases for understanding the unconventional pair-breaking effect responsible for the first-order transition. © 2014 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We investigate the specific heat of ultra pure single crystals of Sr2RuO4, a leading candidate spin-triplet superconductor. For the fi rst time, we obtained specific-heat evidence of the first-order superconducting transition below 0.8 K, namely, divergent-like peaks and clear hysteresis in the specific heat at the upper critical field. The first-order occurs for all in-plane field directions. The specific-heat features for the first-order transition are found to be sensitive to sample quality; in particular, the hysteresis totally disappears in a sample with slightly lower quality. These thermodynamic observations provide crucial bases for understanding the unconventional pair-breaking effect responsible for the first-order transition. © 2014 The Physical Society of Japan.
765.
H Takatsu, G Nénert, H Kadowaki, H Yoshizawa, M Enderle, S Yonezawa, Y Maeno, J Kim, N Tsuji, M Takata, Y Zhao, M Green, C Broholm
Magnetic structure of the conductive triangular-lattice antiferromagnet PdCrO 2 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 89, no. 10, 2014.
@article{Takatsu2014,
title = {Magnetic structure of the conductive triangular-lattice antiferromagnet PdCrO 2},
author = {H Takatsu and G Nénert and H Kadowaki and H Yoshizawa and M Enderle and S Yonezawa and Y Maeno and J Kim and N Tsuji and M Takata and Y Zhao and M Green and C Broholm},
doi = {10.1103/PhysRevB.89.104408},
year = {2014},
date = {2014-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {89},
number = {10},
abstract = {We performed neutron single-crystal and synchrotron x-ray powder diffraction experiments in order to investigate the magnetic and crystal structures of the conductive layered triangular-lattice antiferromagnet PdCrO2 with a putative spin chirality, which contributes to an unconventional anomalous Hall effect. We revealed that the ground-state magnetic structure is a commensurate and nearly coplanar 120â̂̃ spin structure. The 120â̂̃ planes in different Cr layers seem to tilt with one another, leading to a small noncoplanarity. Such a small but finite noncoplanar stacking of the 120â̂̃ planes gives rise to a finite scalar spin chirality, which may be responsible for the unconventional nature of the Hall effect of PdCrO2. © 2014 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We performed neutron single-crystal and synchrotron x-ray powder diffraction experiments in order to investigate the magnetic and crystal structures of the conductive layered triangular-lattice antiferromagnet PdCrO2 with a putative spin chirality, which contributes to an unconventional anomalous Hall effect. We revealed that the ground-state magnetic structure is a commensurate and nearly coplanar 120â̂̃ spin structure. The 120â̂̃ planes in different Cr layers seem to tilt with one another, leading to a small noncoplanarity. Such a small but finite noncoplanar stacking of the 120â̂̃ planes gives rise to a finite scalar spin chirality, which may be responsible for the unconventional nature of the Hall effect of PdCrO2. © 2014 American Physical Society.
764.
K Ueno, T Nojima, S Yonezawa, M Kawasaki, Y Iwasa, Y Maeno
Effective thickness of two-dimensional superconductivity in a tunable triangular quantum well of SrTiO3 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 89, no. 2, 2014.
@article{Ueno2014,
title = {Effective thickness of two-dimensional superconductivity in a tunable triangular quantum well of SrTiO3},
author = {K Ueno and T Nojima and S Yonezawa and M Kawasaki and Y Iwasa and Y Maeno},
doi = {10.1103/PhysRevB.89.020508},
year = {2014},
date = {2014-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {89},
number = {2},
abstract = {We report two-dimensionality and effective thickness of the superconductivity of a SrTiO3 single-crystal surface induced by electric double-layer gating. The carrier density was tuned from 3 × 1013 to 1.1 × 1014 cm-2 by gating, where superconductivity appears with Tc of around 0.4 K. Typical two-dimensional behavior perfectly described by the Ginzburg-Landau equation was observed in the angular and temperature dependence of the upper critical magnetic field. The effective thickness of the superconducting layer remains nearly invariant, ranging from 11 to 13 nm, with increasing charge carrier density. This invariance contradicts the expected reduction in the thickness of the accumulation layer in a triangular quantum well model. This unexpected invariance of the superconducting layer thickness is probably a unique nature for a two-dimensional electron system in the incipient ferroelectric SrTiO 3. © 2014 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report two-dimensionality and effective thickness of the superconductivity of a SrTiO3 single-crystal surface induced by electric double-layer gating. The carrier density was tuned from 3 × 1013 to 1.1 × 1014 cm-2 by gating, where superconductivity appears with Tc of around 0.4 K. Typical two-dimensional behavior perfectly described by the Ginzburg-Landau equation was observed in the angular and temperature dependence of the upper critical magnetic field. The effective thickness of the superconducting layer remains nearly invariant, ranging from 11 to 13 nm, with increasing charge carrier density. This invariance contradicts the expected reduction in the thickness of the accumulation layer in a triangular quantum well model. This unexpected invariance of the superconducting layer thickness is probably a unique nature for a two-dimensional electron system in the incipient ferroelectric SrTiO 3. © 2014 American Physical Society.
763.
R Ishiguro, T Sakurai, M Yakabe, T Nakamura, S Yonezawa, S Kashiwaya, H Takayanagi, Y Maeno
Broken time-reversal symmetry in a SQUID based on chiral superconducting Sr2RuO4 Conference
vol. 568, 2014.
@conference{Ishiguro2014,
title = {Broken time-reversal symmetry in a SQUID based on chiral superconducting Sr2RuO4},
author = {R Ishiguro and T Sakurai and M Yakabe and T Nakamura and S Yonezawa and S Kashiwaya and H Takayanagi and Y Maeno},
doi = {10.1088/1742-6596/568/2/022020},
year = {2014},
date = {2014-01-01},
journal = {Journal of Physics: Conference Series},
volume = {568},
abstract = {Unconventional superconductors involve not only gauge-symmetry breaking but also orbital- and spin-symmetry breaking. Superconducting Sr2RuO4 is known as a spin-triplet chiral p-wave and a topological superconductor with broken time-reversal symmetry (BTRS). Kerr-effect and muon-spin-rotation (pSR) measurements have shown that The bulk superconducting state of Sr2RuO4 features BTRS in The orbital part; hence, it is called The chiral state. BTRS in The response of superconducting junctions or SQUIDs would appear as The shifts of magnetic interference patterns. However, it is problematic to distinguish whether The shift originates in The residual magnetic field (trapped vortex) or The effects of BTRS. Here, we show that The magnetic interference patterns of a SQUID based on Sr2RuO4 are explicitly asymmetric with respect to The direction of both The bias current and The applied magnetic field; namely, there is no inversion symmetry. This indicates that The superconducting state of Sr2RuO4 undoubtedly breaks The time-reversal symmetry of The SQUID. © Published under licence by IOP Publishing Ltd.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Unconventional superconductors involve not only gauge-symmetry breaking but also orbital- and spin-symmetry breaking. Superconducting Sr2RuO4 is known as a spin-triplet chiral p-wave and a topological superconductor with broken time-reversal symmetry (BTRS). Kerr-effect and muon-spin-rotation (pSR) measurements have shown that The bulk superconducting state of Sr2RuO4 features BTRS in The orbital part; hence, it is called The chiral state. BTRS in The response of superconducting junctions or SQUIDs would appear as The shifts of magnetic interference patterns. However, it is problematic to distinguish whether The shift originates in The residual magnetic field (trapped vortex) or The effects of BTRS. Here, we show that The magnetic interference patterns of a SQUID based on Sr2RuO4 are explicitly asymmetric with respect to The direction of both The bias current and The applied magnetic field; namely, there is no inversion symmetry. This indicates that The superconducting state of Sr2RuO4 undoubtedly breaks The time-reversal symmetry of The SQUID. © Published under licence by IOP Publishing Ltd.
762.
Y Nago, R Ishiguro, T Sakurai, M Yakabe, T Nakamura, S Yonezawa, S Kashiwaya, H Takayanagi, Y Maeno
Superconducting transition of Ru in SQUIDs with Nb/Ru/Sr2RuO4 junctions Conference
vol. 568, 2014.
@conference{Nago2014,
title = {Superconducting transition of Ru in SQUIDs with Nb/Ru/Sr2RuO4 junctions},
author = {Y Nago and R Ishiguro and T Sakurai and M Yakabe and T Nakamura and S Yonezawa and S Kashiwaya and H Takayanagi and Y Maeno},
doi = {10.1088/1742-6596/568/2/022031},
year = {2014},
date = {2014-01-01},
journal = {Journal of Physics: Conference Series},
volume = {568},
abstract = {We have measured transport properties and magnetic responses of direct current superconducting quantum interference devices(dc-SQUIDs) with Nb/Ru/Sr2RuO4 junctions on The same Ru inclusion of a Sr2RuO4-Ru eutectic crystal. We observed a superconducting transition of The Ru at 0.50 K and another transition with anomalous interference patterns of The SQUID at 0.40 K. The second transition led to change of The SQUID structure due to energy competition of alternative supercurrent paths. Phase shifts of The peak of The Fraunhofer diffraction pattern were observed below The transition temperatures, implying topological effects due to a chiral p-wave state or its competition with a s-wave state. © Published under licence by IOP Publishing Ltd.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
We have measured transport properties and magnetic responses of direct current superconducting quantum interference devices(dc-SQUIDs) with Nb/Ru/Sr2RuO4 junctions on The same Ru inclusion of a Sr2RuO4-Ru eutectic crystal. We observed a superconducting transition of The Ru at 0.50 K and another transition with anomalous interference patterns of The SQUID at 0.40 K. The second transition led to change of The SQUID structure due to energy competition of alternative supercurrent paths. Phase shifts of The peak of The Fraunhofer diffraction pattern were observed below The transition temperatures, implying topological effects due to a chiral p-wave state or its competition with a s-wave state. © Published under licence by IOP Publishing Ltd.
761.
C W Hicks, D O Brodsky, E A Yelland, A S Gibbs, J A N Bruin, M E Barber, S D Edkins, K Nishimura, S Yonezawa, Y Maeno, A P Mackenzie
Strong increase of Tc of Sr2RuO4under both tensile and compressive strain Journal Article
In: Science, vol. 344, no. 6181, pp. 283-285, 2014.
@article{Hicks2014283,
title = {Strong increase of Tc of Sr2RuO4under both tensile and compressive strain},
author = {C W Hicks and D O Brodsky and E A Yelland and A S Gibbs and J A N Bruin and M E Barber and S D Edkins and K Nishimura and S Yonezawa and Y Maeno and A P Mackenzie},
doi = {10.1126/science.1248292},
year = {2014},
date = {2014-01-01},
journal = {Science},
volume = {344},
number = {6181},
pages = {283-285},
abstract = {A sensitive probe of unconventional order is its response to a symmetry-breaking field. To probe the proposed px ± ip y topological superconducting state of Sr2RuO4, we have constructed an apparatus capable of applying both compressive and tensile strains of up to 0.23%. Strains applied along 〈100〉 crystallographic directions yield a strong, strain-symmetric increase in the superconducting transition temperature Tc• 〈110〉 strains give a much weaker, mostly antisymmetric response. As well as advancing the understanding of the superconductivity of Sr2RuO4, our technique has potential applicability to a wide range of problems in solid-state physics.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A sensitive probe of unconventional order is its response to a symmetry-breaking field. To probe the proposed px ± ip y topological superconducting state of Sr2RuO4, we have constructed an apparatus capable of applying both compressive and tensile strains of up to 0.23%. Strains applied along 〈100〉 crystallographic directions yield a strong, strain-symmetric increase in the superconducting transition temperature Tc• 〈110〉 strains give a much weaker, mostly antisymmetric response. As well as advancing the understanding of the superconductivity of Sr2RuO4, our technique has potential applicability to a wide range of problems in solid-state physics.
760.
R Ishiguro, E Watanabe, D Sakuma, T Shinozaki, S Tsuchiya, Y Nago, H Osato, D Tsuya, H Kashiwaya, S Kashiwaya, S Nomura, H Takayanagi, Y Maeno
Development of nano and micro SQUIDs based on Al tunnel junctions Conference
vol. 568, 2014.
@conference{Ishiguro2014b,
title = {Development of nano and micro SQUIDs based on Al tunnel junctions},
author = {R Ishiguro and E Watanabe and D Sakuma and T Shinozaki and S Tsuchiya and Y Nago and H Osato and D Tsuya and H Kashiwaya and S Kashiwaya and S Nomura and H Takayanagi and Y Maeno},
doi = {10.1088/1742-6596/568/2/022019},
year = {2014},
date = {2014-01-01},
journal = {Journal of Physics: Conference Series},
volume = {568},
abstract = {Superconducting quantum interference devices (SQUIDs) with nano (micro)-meter dimensions are called nano (micro)-SQUIDs. The high sensitivity for flux and position of nano (micro)-SQUIDs can be applied to detect local magnetic fields induced by vortices and The magnetization of mesoscopic superconductors. Nano-SQUIDs based on carbon-nanotube junctions and niobium weak junctions are well known. However, such nano-SQUIDs are not suitable for large-scale integrated circuits and mass production. Therefore, we employ a combination of lithography using The Niemeyer-Dolan technique and The inductively coupled plasma reactive-ion etching technique to fabricate nano-SQUIDs. Here, we report The fabrication of nano (micro)-SQUIDs based on superconducting aluminum tunnel junctions and their application for vortex formation into mesoscopic chiral superconducting Sr2RuO4[1-3]. © Published under licence by IOP Publishing Ltd.},
keywords = {},
pubstate = {published},
tppubtype = {conference}
}
Superconducting quantum interference devices (SQUIDs) with nano (micro)-meter dimensions are called nano (micro)-SQUIDs. The high sensitivity for flux and position of nano (micro)-SQUIDs can be applied to detect local magnetic fields induced by vortices and The magnetization of mesoscopic superconductors. Nano-SQUIDs based on carbon-nanotube junctions and niobium weak junctions are well known. However, such nano-SQUIDs are not suitable for large-scale integrated circuits and mass production. Therefore, we employ a combination of lithography using The Niemeyer-Dolan technique and The inductively coupled plasma reactive-ion etching technique to fabricate nano-SQUIDs. Here, we report The fabrication of nano (micro)-SQUIDs based on superconducting aluminum tunnel junctions and their application for vortex formation into mesoscopic chiral superconducting Sr2RuO4[1-3]. © Published under licence by IOP Publishing Ltd.
759.
K Karube, S Kitagawa, T Hattori, K Ishida, N Kimura, T Komatsubara
Anisotropic uniaxial pressure response in UCoAl studied by nuclear magnetic resonance measurement Journal Article
In: Journal of the Physical Society of Japan, vol. 83, no. 8, 2014.
@article{Karube2014,
title = {Anisotropic uniaxial pressure response in UCoAl studied by nuclear magnetic resonance measurement},
author = {K Karube and S Kitagawa and T Hattori and K Ishida and N Kimura and T Komatsubara},
doi = {10.7566/JPSJ.83.084706},
year = {2014},
date = {2014-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {83},
number = {8},
abstract = {We have performed nuclear quadrupole resonance and nuclear magnetic resonance measurements on UCoAl with strong Ising-type anisotropy under b- and c-axes uniaxial pressure. In the b-axis uniaxial pressure ( P∥b) measurement, we observed an increase in the metamagnetic transition field with increasing P∥b. In the c-axis uniaxial pressure (P∥b) measurement, on the other hand, we observed a ferromagnetic transition in zero magnetic field along the c-axis above P∥c= 0.08 GPa. The anomaly of the nuclear spin-lattice relaxation rate divided by the temperature [(T1T)-1] at T = 20 K is suppressed by P∥band slightly enhanced by P∥c. The anisotropic uniaxial pressure response indicates that uniaxial pressure is a good parameter for tuning the Ising magnetism in UCoAl. © 2014 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We have performed nuclear quadrupole resonance and nuclear magnetic resonance measurements on UCoAl with strong Ising-type anisotropy under b- and c-axes uniaxial pressure. In the b-axis uniaxial pressure ( P∥b) measurement, we observed an increase in the metamagnetic transition field with increasing P∥b. In the c-axis uniaxial pressure (P∥b) measurement, on the other hand, we observed a ferromagnetic transition in zero magnetic field along the c-axis above P∥c= 0.08 GPa. The anomaly of the nuclear spin-lattice relaxation rate divided by the temperature [(T1T)-1] at T = 20 K is suppressed by P∥band slightly enhanced by P∥c. The anisotropic uniaxial pressure response indicates that uniaxial pressure is a good parameter for tuning the Ising magnetism in UCoAl. © 2014 The Physical Society of Japan.
758.
T Hattori, K Karube, K Ishida, K Deguchi, N K Sato, T Yamamura
Relationship between ferromagnetic criticality and the enhancement of superconductivity induced by transverse magnetic fields in UCoGe Journal Article
In: Journal of the Physical Society of Japan, vol. 83, no. 7, 2014.
@article{Hattori2014,
title = {Relationship between ferromagnetic criticality and the enhancement of superconductivity induced by transverse magnetic fields in UCoGe},
author = {T Hattori and K Karube and K Ishida and K Deguchi and N K Sato and T Yamamura},
doi = {10.7566/JPSJ.83.073708},
year = {2014},
date = {2014-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {83},
number = {7},
abstract = {We have performed59Co NMR experiments on the ferromagnetic superconductor UCoGe under magnetic fields (H) along the a- and b-axes to investigate the relationship between ferromagnetic properties and superconductivity. The ferromagnetic ordering temperature TCurie is suppressed and the nuclear spin-lattice relaxation rate 1/T1at 2K is enhanced in H ∥ b, although TCurie and 1/T1are unchanged in H ∥ a, indicating that the ferromagnetic criticality is induced only when H is applied along the b-axis. We show the close relationship between the magnetic anisotropies and the superconducting ones reported by Aoki et al.: the superconductivity is gradually suppressed in H ∥ a, but enhanced in H ∥ b above 5 T. We strongly suggest that the enhancement of the superconductivity observed in H ∥ b originates from the field induced ferromagnetic criticality, as pointed out by Aoki et al. and Mineev. © 2014 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We have performed59Co NMR experiments on the ferromagnetic superconductor UCoGe under magnetic fields (H) along the a- and b-axes to investigate the relationship between ferromagnetic properties and superconductivity. The ferromagnetic ordering temperature TCurie is suppressed and the nuclear spin-lattice relaxation rate 1/T1at 2K is enhanced in H ∥ b, although TCurie and 1/T1are unchanged in H ∥ a, indicating that the ferromagnetic criticality is induced only when H is applied along the b-axis. We show the close relationship between the magnetic anisotropies and the superconducting ones reported by Aoki et al.: the superconductivity is gradually suppressed in H ∥ a, but enhanced in H ∥ b above 5 T. We strongly suggest that the enhancement of the superconductivity observed in H ∥ b originates from the field induced ferromagnetic criticality, as pointed out by Aoki et al. and Mineev. © 2014 The Physical Society of Japan.
757.
T Hattori, Y Ihara, K Karube, D Sugimoto, K Ishida, K Deguchi, N K Sato, T Yamamura
Spin-triplet superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe probed by59Co NMR measurement Journal Article
In: Journal of the Physical Society of Japan, vol. 83, no. 6, 2014.
@article{Hattori2014b,
title = {Spin-triplet superconductivity induced by longitudinal ferromagnetic fluctuations in UCoGe probed by59Co NMR measurement},
author = {T Hattori and Y Ihara and K Karube and D Sugimoto and K Ishida and K Deguchi and N K Sato and T Yamamura},
doi = {10.7566/JPSJ.83.061012},
year = {2014},
date = {2014-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {83},
number = {6},
abstract = {In this review, we present a summary of our experimental results suggesting that the superconducting ferromagnet UCoGe is a spin-triplet superconductor, along with some of the basic physical properties of UCoGe in the normal state. We show experimental evidence that superconductivity in UCoGe is mediated by longitudinal ferromagnetic fluctuations predominant above the superconducting-transition temperature TSC. This is obtained from the tuning of ferromagnetic fluctuations and superconductivity by changing the external field along the magnetic easy axis, the c-axis. In addition, we show that the spin susceptibility perpendicular to the spontaneous magnetic moment, which is probed by Knight-shift measurement, is almost constant in the superconducting state. The behavior of the susceptibility and the invariance of the spontaneous moment below TSCcan be consistently explained by the equal-spin pairing state with a large exchange field along the c-axis. © 2014 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
In this review, we present a summary of our experimental results suggesting that the superconducting ferromagnet UCoGe is a spin-triplet superconductor, along with some of the basic physical properties of UCoGe in the normal state. We show experimental evidence that superconductivity in UCoGe is mediated by longitudinal ferromagnetic fluctuations predominant above the superconducting-transition temperature TSC. This is obtained from the tuning of ferromagnetic fluctuations and superconductivity by changing the external field along the magnetic easy axis, the c-axis. In addition, we show that the spin susceptibility perpendicular to the spontaneous magnetic moment, which is probed by Knight-shift measurement, is almost constant in the superconducting state. The behavior of the susceptibility and the invariance of the spontaneous moment below TSCcan be consistently explained by the equal-spin pairing state with a large exchange field along the c-axis. © 2014 The Physical Society of Japan.
756.
S Kitagawa, T Iye, Y Nakai, K Ishida, C Wang, G -H Cao, Z -A Xu
Relationship between superconductivity and antiferromagnetism in LaFe(As1-xPx)O revealed by 31P-NMR Journal Article
In: Journal of the Physical Society of Japan, vol. 83, no. 2, 2014.
@article{Kitagawa2014,
title = {Relationship between superconductivity and antiferromagnetism in LaFe(As1-xPx)O revealed by 31P-NMR},
author = {S Kitagawa and T Iye and Y Nakai and K Ishida and C Wang and G -H Cao and Z -A Xu},
doi = {10.7566/JPSJ.83.023707},
year = {2014},
date = {2014-01-01},
journal = {Journal of the Physical Society of Japan},
volume = {83},
number = {2},
abstract = {We performed 31P-NMR measurements on LaFe(As1-xP x)O to investigate the relationship between antiferromagnetism and superconductivity. The antiferromagnetic (AFM) ordering temperature T N and the moment μord are continuously suppressed with increasing P content x and disappear at x = 0.3 where bulk superconductivity appears. At this superconducting x = 0.3, quantum critical AFM fluctuations are observed, indicative of the intimate relationship between superconductivity and low-energy AFM fluctuations associated with the quantum-critical point in LaFe(As 1-xPx)O. The relationship is similar to those observed in other isovalent-substitution systems, e.g., BaFe2(As 1-xPx)2 and SrFe2(As 1-xPx)2, with the "122" structure. Moreover, the AFM order reappears with further P substitution (x 0.4). The variation of the ground state with respect to the P substitution is considered to be linked to the change in the band character of Fe-3d orbitals around the Fermi level. © 2014 The Physical Society of Japan.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We performed 31P-NMR measurements on LaFe(As1-xP x)O to investigate the relationship between antiferromagnetism and superconductivity. The antiferromagnetic (AFM) ordering temperature T N and the moment μord are continuously suppressed with increasing P content x and disappear at x = 0.3 where bulk superconductivity appears. At this superconducting x = 0.3, quantum critical AFM fluctuations are observed, indicative of the intimate relationship between superconductivity and low-energy AFM fluctuations associated with the quantum-critical point in LaFe(As 1-xPx)O. The relationship is similar to those observed in other isovalent-substitution systems, e.g., BaFe2(As 1-xPx)2 and SrFe2(As 1-xPx)2, with the "122" structure. Moreover, the AFM order reappears with further P substitution (x 0.4). The variation of the ground state with respect to the P substitution is considered to be linked to the change in the band character of Fe-3d orbitals around the Fermi level. © 2014 The Physical Society of Japan.
2013
755.
C N Veenstra, Z -H Zhu, M Raichle, B M Ludbrook, A Nicolaou, B Slomski, G Landolt, S Kittaka, Y Maeno, J H Dil, I S Elfimov, M W Haverkort, A Damascelli
Spin-orbital entanglement and the breakdown of Singlets and triplets in Sr2RuO4 revealed by spin- and angle-resolved photoemission spectroscopy Journal Article
In: Physical Review Letters, vol. 112, no. 12, 2013.
@article{Veenstra2013,
title = {Spin-orbital entanglement and the breakdown of Singlets and triplets in Sr2RuO4 revealed by spin- and angle-resolved photoemission spectroscopy},
author = {C N Veenstra and Z -H Zhu and M Raichle and B M Ludbrook and A Nicolaou and B Slomski and G Landolt and S Kittaka and Y Maeno and J H Dil and I S Elfimov and M W Haverkort and A Damascelli},
doi = {10.1103/PhysRevLett.112.127002},
year = {2013},
date = {2013-01-01},
journal = {Physical Review Letters},
volume = {112},
number = {12},
abstract = {Spin-orbit coupling has been conjectured to play a key role in the low-energy electronic structure of Sr2RuO4. By using circularly polarized light combined with spin- and angle-resolved photoemission spectroscopy, we directly measure the value of the effective spin-orbit coupling to be 130±30meV. This is even larger than theoretically predicted and comparable to the energy splitting of the dxy and dxz,yz orbitals around the Fermi surface, resulting in a strongly momentum-dependent entanglement of spin and orbital character in the electronic wavefunction. As demonstrated by the spin expectation value sk·s calculated for a pair of electrons with zero total momentum, the classification of the Cooper pairs in terms of pure singlets or triplets fundamentally breaks down, necessitating a description of the unconventional superconducting state of Sr2RuO4 in terms of these newly found spin-orbital entangled eigenstates. © 2014 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Spin-orbit coupling has been conjectured to play a key role in the low-energy electronic structure of Sr2RuO4. By using circularly polarized light combined with spin- and angle-resolved photoemission spectroscopy, we directly measure the value of the effective spin-orbit coupling to be 130±30meV. This is even larger than theoretically predicted and comparable to the energy splitting of the dxy and dxz,yz orbitals around the Fermi surface, resulting in a strongly momentum-dependent entanglement of spin and orbital character in the electronic wavefunction. As demonstrated by the spin expectation value sk·s calculated for a pair of electrons with zero total momentum, the classification of the Cooper pairs in terms of pure singlets or triplets fundamentally breaks down, necessitating a description of the unconventional superconducting state of Sr2RuO4 in terms of these newly found spin-orbital entangled eigenstates. © 2014 American Physical Society.
754.
S Yonezawa, Y Maeno
Transport properties of Ag5Pb2O6: A three-dimensional electron-gas-like system with low carrier density Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 88, no. 20, 2013.
@article{Yonezawa2013,
title = {Transport properties of Ag5Pb2O6: A three-dimensional electron-gas-like system with low carrier density},
author = {S Yonezawa and Y Maeno},
doi = {10.1103/PhysRevB.88.205143},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {88},
number = {20},
abstract = {We report normal-state transport properties of the single-crystalline samples of the silver-lead oxide superconductor Ag5Pb 2O6, including the electrical resistivity, magnetoresistance, and Hall coefficient. From the Hall coefficient measurement, we confirmed that the carrier density of this oxide is as low as 5×1021 cm-3, one order of magnitude smaller than that for ordinary alkali metals and noble metals. The magnetoresistance behavior is well characterized by the axial symmetry of the Fermi surface and by a single relaxation time. The T2 term of the resistivity is scaled with the specific-heat coefficient, based on the recent theory for the electron-electron scattering. The present results provide evidence that Ag5Pb2O6 is a low-carrier-density three-dimensional electron-gas-like system with enhanced electron-electron scatterings. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report normal-state transport properties of the single-crystalline samples of the silver-lead oxide superconductor Ag5Pb 2O6, including the electrical resistivity, magnetoresistance, and Hall coefficient. From the Hall coefficient measurement, we confirmed that the carrier density of this oxide is as low as 5×1021 cm-3, one order of magnitude smaller than that for ordinary alkali metals and noble metals. The magnetoresistance behavior is well characterized by the axial symmetry of the Fermi surface and by a single relaxation time. The T2 term of the resistivity is scaled with the specific-heat coefficient, based on the recent theory for the electron-electron scattering. The present results provide evidence that Ag5Pb2O6 is a low-carrier-density three-dimensional electron-gas-like system with enhanced electron-electron scatterings. © 2013 American Physical Society.
753.
H Taniguchi, K Nishimura, R Ishikawa, S Yonezawa, S K Goh, F Nakamura, Y Maeno
Anisotropic uniaxial pressure response of the Mott insulator Ca 2RuO4 Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 88, no. 20, 2013.
@article{Taniguchi2013,
title = {Anisotropic uniaxial pressure response of the Mott insulator Ca 2RuO4},
author = {H Taniguchi and K Nishimura and R Ishikawa and S Yonezawa and S K Goh and F Nakamura and Y Maeno},
doi = {10.1103/PhysRevB.88.205111},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {88},
number = {20},
abstract = {We have investigated the in-plane uniaxial pressure effect on the antiferromagnetic Mott insulator Ca2RuO4 from resistivity and magnetization measurements. We succeeded in inducing the ferromagnetic metallic phase at lower critical pressure than by hydrostatic pressure, indicating that the flattening distortion of the RuO6 octahedra is more easily released under in-plane uniaxial pressure. We also found a striking in-plane anisotropy in the pressure responses of various magnetic phases: although the magnetization increases monotonically with pressure diagonal to the orthorhombic principal axes, the magnetization exhibits peculiar dependence on pressure along the in-plane orthorhombic principal axes. This peculiar dependence can be explained by a qualitative difference between the uniaxial pressure effects along the orthorhombic a and b axes, as well as by the presence of twin domain structures. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We have investigated the in-plane uniaxial pressure effect on the antiferromagnetic Mott insulator Ca2RuO4 from resistivity and magnetization measurements. We succeeded in inducing the ferromagnetic metallic phase at lower critical pressure than by hydrostatic pressure, indicating that the flattening distortion of the RuO6 octahedra is more easily released under in-plane uniaxial pressure. We also found a striking in-plane anisotropy in the pressure responses of various magnetic phases: although the magnetization increases monotonically with pressure diagonal to the orthorhombic principal axes, the magnetization exhibits peculiar dependence on pressure along the in-plane orthorhombic principal axes. This peculiar dependence can be explained by a qualitative difference between the uniaxial pressure effects along the orthorhombic a and b axes, as well as by the presence of twin domain structures. © 2013 American Physical Society.
752.
J A Sobota, K Kim, H Takatsu, M Hashimoto, S -K Mo, Z Hussain, T Oguchi, T Shishidou, Y Maeno, B I Min, Z -X Shen
Electronic structure of the metallic antiferromagnet PdCrO2 measured by angle-resolved photoemission spectroscopy Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 88, no. 12, 2013.
@article{Sobota2013,
title = {Electronic structure of the metallic antiferromagnet PdCrO2 measured by angle-resolved photoemission spectroscopy},
author = {J A Sobota and K Kim and H Takatsu and M Hashimoto and S -K Mo and Z Hussain and T Oguchi and T Shishidou and Y Maeno and B I Min and Z -X Shen},
doi = {10.1103/PhysRevB.88.125109},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {88},
number = {12},
abstract = {PdCrO2 is material which has attracted interest due to the coexistence of metallic conductivity associated with itinerant Pd 4d electrons and antiferromagnetic order arising from localized Cr spins. A central issue is determining to what extent the magnetic order couples to the conduction electrons. Here we perform angle-resolved photoemission spectroscopy (ARPES) to experimentally characterize the electronic structure. We find that the Fermi surface has contributions from both bulk and surface states, which can be experimentally distinguished and theoretically verified by slab band structure calculations. The bulk Fermi surface shows no signature of electronic reconstruction in the antiferromagnetic state. This observation suggests that there is negligible interaction between the localized Cr spin structure and the itinerant Pd electrons measured by ARPES. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
PdCrO2 is material which has attracted interest due to the coexistence of metallic conductivity associated with itinerant Pd 4d electrons and antiferromagnetic order arising from localized Cr spins. A central issue is determining to what extent the magnetic order couples to the conduction electrons. Here we perform angle-resolved photoemission spectroscopy (ARPES) to experimentally characterize the electronic structure. We find that the Fermi surface has contributions from both bulk and surface states, which can be experimentally distinguished and theoretically verified by slab band structure calculations. The bulk Fermi surface shows no signature of electronic reconstruction in the antiferromagnetic state. This observation suggests that there is negligible interaction between the localized Cr spin structure and the itinerant Pd electrons measured by ARPES. © 2013 American Physical Society.
751.
M S Anwar, T Nakamura, S Yonezawa, M Yakabe, R Ishiguro, H Takayanagi, Y Maeno
Anomalous switching in Nb/Ru/Sr2 RuO4 topological junctions by chiral domain wall motion Journal Article
In: Scientific Reports, vol. 3, 2013.
@article{Anwar2013,
title = {Anomalous switching in Nb/Ru/Sr2 RuO4 topological junctions by chiral domain wall motion},
author = {M S Anwar and T Nakamura and S Yonezawa and M Yakabe and R Ishiguro and H Takayanagi and Y Maeno},
doi = {10.1038/srep02480},
year = {2013},
date = {2013-01-01},
journal = {Scientific Reports},
volume = {3},
abstract = {A spontaneous symmetry breaking in a system often results in domain wall formation. The motion of such domain walls is utilized to realize novel devices like racetrack-memories, in which moving ferromagnetic domain walls store and carry information. Superconductors breaking time reversal symmetry can also form domains with degenerate chirality of their superconducting order parameter. Sr2 RuO4 is the leading candidate of a chiral p-wave superconductor, expected to be accompanied by chiral domain structure. Here, we present that Nb/Ru/Sr2 RuO4 topological superconducting-junctions, with which the phase winding of order parameter can be effectively probed by making use of real-space topology, exhibit unusual switching between higher and lower critical current states. This switching is well explained by chiral-domain-wall dynamics. The switching can be partly controlled by external parameters such as temperature, magnetic field and current. These results open up a possibility to utilize the superconducting chiral domain wall motion for future novel superconducting devices. © 2013 Macmillan Publishers Limited.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
A spontaneous symmetry breaking in a system often results in domain wall formation. The motion of such domain walls is utilized to realize novel devices like racetrack-memories, in which moving ferromagnetic domain walls store and carry information. Superconductors breaking time reversal symmetry can also form domains with degenerate chirality of their superconducting order parameter. Sr2 RuO4 is the leading candidate of a chiral p-wave superconductor, expected to be accompanied by chiral domain structure. Here, we present that Nb/Ru/Sr2 RuO4 topological superconducting-junctions, with which the phase winding of order parameter can be effectively probed by making use of real-space topology, exhibit unusual switching between higher and lower critical current states. This switching is well explained by chiral-domain-wall dynamics. The switching can be partly controlled by external parameters such as temperature, magnetic field and current. These results open up a possibility to utilize the superconducting chiral domain wall motion for future novel superconducting devices. © 2013 Macmillan Publishers Limited.
750.
F Nakamura, M Sakaki, Y Yamanaka, S Tamaru, T Suzuki, Y Maeno
Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4 Journal Article
In: Scientific Reports, vol. 3, 2013.
@article{Nakamura2013,
title = {Electric-field-induced metal maintained by current of the Mott insulator Ca2RuO4},
author = {F Nakamura and M Sakaki and Y Yamanaka and S Tamaru and T Suzuki and Y Maeno},
doi = {10.1038/srep02536},
year = {2013},
date = {2013-01-01},
journal = {Scientific Reports},
volume = {3},
abstract = {Recently, "application of electric field (E-field)" has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature. The threshold field Eth ∼40 V/cm is much weaker than the Mott gap energy. Moreover, the switching is accompanied by a bulk structural transition. Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Recently, "application of electric field (E-field)" has received considerable attention as a new method to induce novel quantum phenomena since application of E-field can tune the electronic states directly with obvious scientific and industrial advantages over other turning methods. However, E-field-induced Mott transitions are rare and typically require high E-field and low temperature. Here we report that the multiband Mott insulator Ca2RuO4 shows unique insulator-metal switching induced by applying a dry-battery level voltage at room temperature. The threshold field Eth ∼40 V/cm is much weaker than the Mott gap energy. Moreover, the switching is accompanied by a bulk structural transition. Perhaps the most peculiar of the present findings is that the induced metal can be maintained to low temperature by a weak current.
749.
C Rastovski, C D Dewhurst, W J Gannon, D C Peets, H Takatsu, Y Maeno, M Ichioka, K Machida, M R Eskildsen
Anisotropy of the superconducting state in Sr2RuO4 Journal Article
In: Physical Review Letters, vol. 111, no. 8, 2013.
@article{Rastovski2013,
title = {Anisotropy of the superconducting state in Sr2RuO4},
author = {C Rastovski and C D Dewhurst and W J Gannon and D C Peets and H Takatsu and Y Maeno and M Ichioka and K Machida and M R Eskildsen},
doi = {10.1103/PhysRevLett.111.087003},
year = {2013},
date = {2013-01-01},
journal = {Physical Review Letters},
volume = {111},
number = {8},
abstract = {Despite intense studies the exact nature of the order parameter in superconducting Sr2RuO4 remains unresolved. We have used small-angle neutron scattering to study the vortex lattice in Sr 2RuO4 with the field applied close to the basal plane, taking advantage of the transverse magnetization. We measured the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane (∼60), which greatly exceeds the upper critical field anisotropy (∼20). Our result imposes significant constraints on possible models of triplet pairing in Sr2RuO4 and raises questions concerning the direction of the zero spin projection axis. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Despite intense studies the exact nature of the order parameter in superconducting Sr2RuO4 remains unresolved. We have used small-angle neutron scattering to study the vortex lattice in Sr 2RuO4 with the field applied close to the basal plane, taking advantage of the transverse magnetization. We measured the intrinsic superconducting anisotropy between the c axis and the Ru-O basal plane (∼60), which greatly exceeds the upper critical field anisotropy (∼20). Our result imposes significant constraints on possible models of triplet pairing in Sr2RuO4 and raises questions concerning the direction of the zero spin projection axis. © 2013 American Physical Society.
748.
H Takatsu, J J Ishikawa, S Yonezawa, H Yoshino, T Shishidou, T Oguchi, K Murata, Y Maeno
Extremely large magnetoresistance in the nonmagnetic metal PdCoO 2 Journal Article
In: Physical Review Letters, vol. 111, no. 5, 2013.
@article{Takatsu2013,
title = {Extremely large magnetoresistance in the nonmagnetic metal PdCoO 2},
author = {H Takatsu and J J Ishikawa and S Yonezawa and H Yoshino and T Shishidou and T Oguchi and K Murata and Y Maeno},
doi = {10.1103/PhysRevLett.111.056601},
year = {2013},
date = {2013-01-01},
journal = {Physical Review Letters},
volume = {111},
number = {5},
abstract = {Extremely large magnetoresistance is realized in the nonmagnetic layered metal PdCoO2. In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35 000% for the field along the [11̄0] direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Extremely large magnetoresistance is realized in the nonmagnetic layered metal PdCoO2. In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35 000% for the field along the [11̄0] direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now. © 2013 American Physical Society.
747.
S Tsuda, N Kikugawa, K Sugii, S Uji, S Ueda, M Nishio, Y Maeno
Mott transition extremely sensitive to impurities in Ca3Ru 2O7 revealed by hard x-ray photoemission studies Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 87, no. 24, 2013.
@article{Tsuda2013,
title = {Mott transition extremely sensitive to impurities in Ca3Ru 2O7 revealed by hard x-ray photoemission studies},
author = {S Tsuda and N Kikugawa and K Sugii and S Uji and S Ueda and M Nishio and Y Maeno},
doi = {10.1103/PhysRevB.87.241107},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {87},
number = {24},
abstract = {Hard x-ray photoemission studies of Ca3(Ru1-xTi x)2O7 with x = 0, 0.003, and 0.005 have been carried out to clarify the origin of the extremely high sensitivity of the metal-insulator (M-I) transition to the amount of Ti substitution. All the compounds show an antiferromagnetic transition followed by a structural transition at a temperature TS, with decreasing temperature. For x > 0, the structural transition is accompanied with a drastic M-I transition and the intensities of the screened peaks in the Ru 3d core-level spectra are significantly reduced below TS. The spectral weight of the valence band is concurrently shifted toward the higher binding energy side by an order of 2 eV, which shows that a strong electron correlation plays an essential role for the M-I transition at TS for x > 0. These results provide strong evidence that Mott transition is induced by a minute amount of the Ti substitution in Ca3Ru2O7. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Hard x-ray photoemission studies of Ca3(Ru1-xTi x)2O7 with x = 0, 0.003, and 0.005 have been carried out to clarify the origin of the extremely high sensitivity of the metal-insulator (M-I) transition to the amount of Ti substitution. All the compounds show an antiferromagnetic transition followed by a structural transition at a temperature TS, with decreasing temperature. For x > 0, the structural transition is accompanied with a drastic M-I transition and the intensities of the screened peaks in the Ru 3d core-level spectra are significantly reduced below TS. The spectral weight of the valence band is concurrently shifted toward the higher binding energy side by an order of 2 eV, which shows that a strong electron correlation plays an essential role for the M-I transition at TS for x > 0. These results provide strong evidence that Mott transition is induced by a minute amount of the Ti substitution in Ca3Ru2O7. © 2013 American Physical Society.
746.
E J Patiño, M Aprili, M G Blamire, Y Maeno
Vortex flipping in superconductor/ferromagnet spin-valve structures Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 87, no. 21, 2013.
@article{Patiño2013,
title = {Vortex flipping in superconductor/ferromagnet spin-valve structures},
author = {E J Patiño and M Aprili and M G Blamire and Y Maeno},
doi = {10.1103/PhysRevB.87.214514},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {87},
number = {21},
abstract = {We report in-plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by ferromagnet magnetization. This is a direct consequence of the proximity effect that leads to vortex supercurrent leakage into the ferromagnets. Here, the polarized electron spins are subject to the vortices' magnetic field, occasioning vortex flipping. Such a novel mechanism has been made possible by fabrication of the ferromagnet/superconductor/ferromagnet/ antiferromagnet multilayered spin valves with an S layer thin enough to barely confine vortices inside as well as F layers thin enough to align and control magnetization within the plane. When Co is used, the vortex flipping effect is not observed. This is attributed to the shorter coherence length of Co. Interestingly, a reduction in the pinning field of about 400 Oe is observed instead when the Nb layer is in the superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts, any explanation must be directly related to the proximity effect and thus a remarkable phenomenon that deserves further investigation. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report in-plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by ferromagnet magnetization. This is a direct consequence of the proximity effect that leads to vortex supercurrent leakage into the ferromagnets. Here, the polarized electron spins are subject to the vortices' magnetic field, occasioning vortex flipping. Such a novel mechanism has been made possible by fabrication of the ferromagnet/superconductor/ferromagnet/ antiferromagnet multilayered spin valves with an S layer thin enough to barely confine vortices inside as well as F layers thin enough to align and control magnetization within the plane. When Co is used, the vortex flipping effect is not observed. This is attributed to the shorter coherence length of Co. Interestingly, a reduction in the pinning field of about 400 Oe is observed instead when the Nb layer is in the superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts, any explanation must be directly related to the proximity effect and thus a remarkable phenomenon that deserves further investigation. © 2013 American Physical Society.
745.
G Bao, Y Inada, G Eguchi, Y Maeno, M Ichioka, G -Q Zheng
Influence on superconductivity in the parity mixing superconductor Li 2T3B(T:Pt,Pd) by non-magnetic impurity and defect doping Journal Article
In: Physica C: Superconductivity and its Applications, vol. 494, pp. 95-98, 2013.
@article{Bao201395,
title = {Influence on superconductivity in the parity mixing superconductor Li 2T3B(T:Pt,Pd) by non-magnetic impurity and defect doping},
author = {G Bao and Y Inada and G Eguchi and Y Maeno and M Ichioka and G -Q Zheng},
doi = {10.1016/j.physc.2013.04.059},
year = {2013},
date = {2013-01-01},
journal = {Physica C: Superconductivity and its Applications},
volume = {494},
pages = {95-98},
abstract = {Superconductors with noncentrosymmetric crystal structures such as Li 2T3B(T:Pd,Pt) have been the focus of in-depth research with their parity mixing nature. In this study, we focused our research on non-magnetic impurity effect in Li2T3B(T:Pd,Pt). The nature of the pair breaking by non-magnetic impurity in the parity mixing superconducting state is still unclear. We prepared different quality samples of Li2Pd3B and Li2Pt3B by changing conditions in synthesizing, and sample qualities were estimated by residual resistivity. Spin singlet dominant superconductor Li2Pd3B exhibits the weak Tc suppression attributed by non-magnetic impurity and defects, while Hc2 (0) value increased. This behavior is similar in ordinary s-wave superconductor. On the other hand, for the spin triplet dominant superconductor Li2Pt3B, it was suggested that the Cooper pair was broken and superconducting gap was decreased by non-magnetic impurities and defects. Li2Pt3B is similar to unconventional superconducting state. © 2013 Elsevier B.V. All rights reserved.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Superconductors with noncentrosymmetric crystal structures such as Li 2T3B(T:Pd,Pt) have been the focus of in-depth research with their parity mixing nature. In this study, we focused our research on non-magnetic impurity effect in Li2T3B(T:Pd,Pt). The nature of the pair breaking by non-magnetic impurity in the parity mixing superconducting state is still unclear. We prepared different quality samples of Li2Pd3B and Li2Pt3B by changing conditions in synthesizing, and sample qualities were estimated by residual resistivity. Spin singlet dominant superconductor Li2Pd3B exhibits the weak Tc suppression attributed by non-magnetic impurity and defects, while Hc2 (0) value increased. This behavior is similar in ordinary s-wave superconductor. On the other hand, for the spin triplet dominant superconductor Li2Pt3B, it was suggested that the Cooper pair was broken and superconducting gap was decreased by non-magnetic impurities and defects. Li2Pt3B is similar to unconventional superconducting state. © 2013 Elsevier B.V. All rights reserved.
744.
G Eguchi, D C Peets, M Kriener, S Yonezawa, G Bao, S Harada, Y Inada, G -Q Zheng, Y Maeno
Phonon anomaly and anisotropic superconducting gap in noncentrosymmetric Li2(Pd1-xPtx)3B Journal Article
In: Physical Review B - Condensed Matter and Materials Physics, vol. 87, no. 16, 2013.
@article{Eguchi2013,
title = {Phonon anomaly and anisotropic superconducting gap in noncentrosymmetric Li2(Pd1-xPtx)3B},
author = {G Eguchi and D C Peets and M Kriener and S Yonezawa and G Bao and S Harada and Y Inada and G -Q Zheng and Y Maeno},
doi = {10.1103/PhysRevB.87.161203},
year = {2013},
date = {2013-01-01},
journal = {Physical Review B - Condensed Matter and Materials Physics},
volume = {87},
number = {16},
abstract = {We report the systematic investigation of the specific heat of the noncentrosymmetric superconductor Li2(Pd1-xPtx)3B as a function of x. There is a large deviation of the phononic specific heat from the conventional Debye specific heat for Pt-rich samples. In contrast with the fully gapped conventional behavior for small x, a power-law temperature dependence of the electronic specific heat is observed even at x=0.5. These results manifest a strongly anisotropic or nodal superconducting gap even at x=0.5 and a nodal superconducting gap for xâ‰30.9. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report the systematic investigation of the specific heat of the noncentrosymmetric superconductor Li2(Pd1-xPtx)3B as a function of x. There is a large deviation of the phononic specific heat from the conventional Debye specific heat for Pt-rich samples. In contrast with the fully gapped conventional behavior for small x, a power-law temperature dependence of the electronic specific heat is observed even at x=0.5. These results manifest a strongly anisotropic or nodal superconducting gap even at x=0.5 and a nodal superconducting gap for xâ‰30.9. © 2013 American Physical Society.
743.
C Stingl, R S Perry, Y Maeno, P Gegenwart
Electronic nematicity and its relation to quantum criticality in Sr3Ru2O7 studied by thermal expansion Journal Article
In: Physica Status Solidi (B) Basic Research, vol. 250, no. 3, pp. 450-456, 2013.
@article{Stingl2013450,
title = {Electronic nematicity and its relation to quantum criticality in Sr3Ru2O7 studied by thermal expansion},
author = {C Stingl and R S Perry and Y Maeno and P Gegenwart},
doi = {10.1002/pssb.201200905},
year = {2013},
date = {2013-01-01},
journal = {Physica Status Solidi (B) Basic Research},
volume = {250},
number = {3},
pages = {450-456},
abstract = {We report high-resolution measurements of the in-plane thermal expansion anisotropy in the vicinity of the electronic nematic phase in Sr3Ru2O7 down to very low temperatures and in varying magnetic field orientation. For fields applied along the c-direction, a clear second-order phase transition is found at the nematic phase, with critical behavior compatible with the two-dimensional Ising universality class (although this is not fully conclusive). Measurements in a slightly tilted magnetic field reveal a broken fourfold in-plane rotational symmetry, not only within the nematic phase, but extending towards slightly larger fields. We also analyze the universal scaling behavior expected for a metamagnetic quantum critical point, which is realized outside the nematic region. The contours of the magnetostriction suggest a relation between quantum criticality and the nematic phase. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We report high-resolution measurements of the in-plane thermal expansion anisotropy in the vicinity of the electronic nematic phase in Sr3Ru2O7 down to very low temperatures and in varying magnetic field orientation. For fields applied along the c-direction, a clear second-order phase transition is found at the nematic phase, with critical behavior compatible with the two-dimensional Ising universality class (although this is not fully conclusive). Measurements in a slightly tilted magnetic field reveal a broken fourfold in-plane rotational symmetry, not only within the nematic phase, but extending towards slightly larger fields. We also analyze the universal scaling behavior expected for a metamagnetic quantum critical point, which is realized outside the nematic region. The contours of the magnetostriction suggest a relation between quantum criticality and the nematic phase. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
742.
C N Veenstra, Z -H Zhu, B Ludbrook, M Capsoni, G Levy, A Nicolaou, J A Rosen, R Comin, S Kittaka, Y Maeno, I S Elfimov, A Damascelli
In: Physical Review Letters, vol. 110, no. 9, 2013.
@article{Veenstra2013b,
title = {Determining the surface-to-bulk progression in the normal-state electronic structure of Sr2RuO4 by angle-resolved photoemission and density functional theory},
author = {C N Veenstra and Z -H Zhu and B Ludbrook and M Capsoni and G Levy and A Nicolaou and J A Rosen and R Comin and S Kittaka and Y Maeno and I S Elfimov and A Damascelli},
doi = {10.1103/PhysRevLett.110.097004},
year = {2013},
date = {2013-01-01},
journal = {Physical Review Letters},
volume = {110},
number = {9},
abstract = {We revisit the normal-state electronic structure of Sr2RuO 4 by angle-resolved photoemission spectroscopy with improved data quality, as well as ab initio band structure calculations in the local-density approximation with the inclusion of spin-orbit coupling. We find that the current model of a single surface layer (√2×√2)R45 reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with the slab calculations based on the surface crystal structure as determined by low-energy electron diffraction, reveal that - at a minimum - the subsurface layer also undergoes a similar although weaker reconstruction. This model accounts for all features - a key step in understanding the electronic structure - and indicates a surface-to-bulk progression of the electronic states driven by structural instabilities. Finally, we find no evidence for other phases stemming from either topological bulk properties or, alternatively, the interplay between spin-orbit coupling and the broken symmetry of the surface. © 2013 American Physical Society.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We revisit the normal-state electronic structure of Sr2RuO 4 by angle-resolved photoemission spectroscopy with improved data quality, as well as ab initio band structure calculations in the local-density approximation with the inclusion of spin-orbit coupling. We find that the current model of a single surface layer (√2×√2)R45 reconstruction does not explain all detected features. The observed depth-dependent signal degradation, together with the close quantitative agreement with the slab calculations based on the surface crystal structure as determined by low-energy electron diffraction, reveal that - at a minimum - the subsurface layer also undergoes a similar although weaker reconstruction. This model accounts for all features - a key step in understanding the electronic structure - and indicates a surface-to-bulk progression of the electronic states driven by structural instabilities. Finally, we find no evidence for other phases stemming from either topological bulk properties or, alternatively, the interplay between spin-orbit coupling and the broken symmetry of the surface. © 2013 American Physical Society.
