論文リスト

@article{Kambara2011708,

title = {Local transport characteristics of break junction in Sr2RuO 4 microbridge},

author = {H Kambara and S Kashiwaya and H Kashiwaya and Y Tanaka and Y Maeno},

doi = {10.1016/j.physc.2011.05.033},

year  = {2011},

date = {2011-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {471},

number = {21-22},

pages = {708-710},

abstract = {We have measured tunnel conductance of spin-triplet superconductor Sr 2RuO4 (SRO) break junction which was made by micro fabrication technique with a focused ion beam. This is a new type of tunnel junctions made of SRO, which is different from those made of SRO and other materials. Since the tunnel conductance is sensitive to the internal phase of superconductivity, it enables us to examine the chiral p-wave pairing state, which is the most probable candidate of SRO. The tunnel conductance spectrum of the junction showed a broad zero-bias conductance peak whose shape is different from that of high-Tc cuprate superconductors. The shape of the spectrum is in quite good agreement with the calculated spectrum of a chiral p-wave/insulator/normal metal junction. © 2011 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Peets2011,

title = {Erratum: Magnetic phase diagram of Li2(Pd1-xPt x)3B by ac susceptometry (Physical Review B (2011) 84 (054521))},

author = {D C Peets and G Eguchi and M Kriener and S Harada and S M Shamsuzzamen and Y Inada and G -Q Zheng and Y Maeno},

doi = {10.1103/PhysRevB.84.059908},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {84},

number = {5},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nakamura2011,

title = {Topological competition of superconductivity in Pb/Ru/Sr 2RuO4 junctions},

author = {T Nakamura and R Nakagawa and T Yamagishi and T Terashima and S Yonezawa and M Sigrist and Y Maeno},

doi = {10.1103/PhysRevB.84.060512},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {84},

number = {6},

abstract = {We devise an unconventional proximity junction configuration where an s-wave superconductivity and the superconductivity of Sr2RuO 4 interfere with each other. We reproducibly observe in such a Pb/Ru/Sr2RuO4 junction with a single Pb electrode that the critical current Ic drops sharply just below the bulk Tc of Sr2RuO4 and furthermore increases again below a certain temperature below Tc. In order to explain this temperature dependence of Ic, we propose a competition effect involving topologically distinct superconducting phases around Ru inclusions. Thus, such a device may be called a topological superconducting junction. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Peets2011b,

title = {Magnetic phase diagram of Li2(Pd1-xPt x)3B by ac susceptometry},

author = {D C Peets and G Eguchi and M Kriener and S Harada and S M Shamsuzzamen and Y Inada and G -Q Zheng and Y Maeno},

doi = {10.1103/PhysRevB.84.054521},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {84},

number = {5},

abstract = {The H-T phase diagram and several superconducting parameters for the noncentrosymmetric system Li2(Pd1-xPtx) 3B have been determined as a function of cation substitution x. Notably, the coherence length may be linear in platinum concentration. Despite the superconducting pairing state and band structure apparently changing fundamentally, the H-T phase diagram is essentially unchanged. Unusual aspects of the shape of the H-T phase diagram are discussed. The upper critical field Hc2(0) is not anomalously high for any Pt content, likely due to an absence of high carrier masses-in such a case, the value of Hc2(0) would not serve as a probe for novel physics. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kashiwaya2011,

title = {Edge states of Sr2RuO4 detected by in-plane tunneling spectroscopy},

author = {S Kashiwaya and H Kashiwaya and H Kambara and T Furuta and H Yaguchi and Y Tanaka and Y Maeno},

doi = {10.1103/PhysRevLett.107.077003},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review Letters},

volume = {107},

number = {7},

abstract = {Tunneling spectroscopy has been performed on Sr2RuO4 searching for the edge states peculiar to topological superconductivity. Conductance spectra exhibit broad humps with three types of peak shape: domelike peak, split peak, and two-step peak. By comparing the experiments with predictions for unconventional superconductivity, these varieties are shown to originate from multiband chiral p-wave symmetry with weak anisotropy of pair amplitude. The broad hump in the conductance spectrum is a direct manifestation of the edge state due to chiral p-wave superconductivity. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Stingl2011,

title = {Symmetry-breaking lattice distortion in Sr3Ru2O 7},

author = {C Stingl and R S Perry and Y Maeno and P Gegenwart},

doi = {10.1103/PhysRevLett.107.026404},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review Letters},

volume = {107},

number = {2},

abstract = {The electronic nematic phase of Sr3Ru2O7 is investigated by high-resolution in-plane thermal expansion measurements in magnetic fields close to 8T applied at various angles Θ off the caxis. At Θ<10° we observe a very small (10⊃-7) lattice distortion which breaks the fourfold in-plane symmetry, resulting in nematic domains with interchanged a and baxis. At Θ≥10° the domains are almost fully aligned and thermal expansion indicates an area-preserving lattice distortion of order 2×10⊃-6 which is likely related to orbital ordering. Since the system is located in the immediate vicinity of a metamagnetic quantum critical end point, the results represent the first observation of a structural relaxation driven by quantum criticality. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ciancio2011324,

title = {Electron backscattering diffraction and X-ray diffraction studies of interface relationships in Sr3Ru2O7/Sr2RuO4 eutectic crystals},

author = {R Ciancio and H Pettersson and R Fittipaldi and A Kalabukhov and P Orgiani and A Vecchione and Y Maeno and S Pace and E Olsson},

doi = {10.1016/j.micron.2010.03.012},

year  = {2011},

date = {2011-01-01},

journal = {Micron},

volume = {42},

number = {4},

pages = {324-329},

abstract = {Sr3Ru2O7/Sr2RuO4 eutectic system is investigated by electron backscattering diffraction (EBSD) and X-ray diffraction (XRD). The eutectic growth enables the solidification of the two phases in an ordered lamellar pattern extending along the growth direction, namely the b-axis direction. The eutectic material thus provides in the a-c plane two distinct interfaces having different microstructures with respect to the growth direction. Our analysis shows that, across the inplane c-axis direction (characterized by a poor lattice matching), the b-axis orientation is not constant at the individual interfaces, showing an orientation spread of about 5° However, across the in-plane a-axis direction (characterized by a good lattice matching), the b-axis orientation does not change within a few tenths of degree (about 0.25°). Such information at nanoscale is also verified on a macroscopic level by standard XRD investigation. © 2010 Elsevier Ltd.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Malvestuto2011,

title = {Electronic structure trends in the Srn+1RunO 3n+1 family (n=1,2,3)},

author = {M Malvestuto and E Carleschi and R Fittipaldi and E Gorelov and E Pavarini and M Cuoco and Y Maeno and F Parmigiani and A Vecchione},

doi = {10.1103/PhysRevB.83.165121},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {83},

number = {16},

abstract = {The identification of electronic states and the analysis of their evolution with n is key to understanding n-layered ruthenates. To this end, we combine polarization-dependent O 1s x-ray absorption spectroscopy, high-purity Sr n+1RunO3n+1 (n=1,2,3) single crystals, and ab initio and many-body calculations. We find that the energy splitting between the empty x2-y2 and 3z2-1 state is considerably smaller than previously suggested and that, remarkably, Sr bands are essential to understanding the spectra. At low energy, we identify the main difference among the materials with a substantial rearrangement of t2g orbital occupations with increasing n. This rearrangement is controlled by the interplay of Coulomb repulsion, dimensionality, and changes in the t2g crystal field. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ishii2011,

title = {Successive phase transitions and phase diagrams for the quasi-two-dimensional easy-axis triangular antiferromagnet Rb 4Mn(MoO4)3},

author = {R Ishii and S Tanaka and K Onuma and Y Nambu and M Tokunaga and T Sakakibara and N Kawashima and Y Maeno and C Broholm and D P Gautreaux and J Y Chan and S Nakatsuji},

doi = {10.1209/0295-5075/94/17001},

year  = {2011},

date = {2011-01-01},

journal = {EPL},

volume = {94},

number = {1},

abstract = {Using magnetic, thermal and neutron measurements we show that Rb 4Mn(MoO4)3 is a quasi-2D triangular Heisenberg antiferromagnet with easy-axis anisotropy and successive transitions bracketing an intermediate collinear phase. An accurate quantitative account of the phase diagram is achieved through Monte Carlo simulation of a spin Hamiltonian with easy-axis anisotropy D=0.22J. © 2011 Europhysics Letters Association.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jang2011,

title = {Phase-locked cantilever magnetometry},

author = {J Jang and R Budakian and Y Maeno},

doi = {10.1063/1.3572026},

year  = {2011},

date = {2011-01-01},

journal = {Applied Physics Letters},

volume = {98},

number = {13},

abstract = {We describe a feedback-based dynamic cantilever magnetometry technique capable of achieving thermal limited magnetic moment sensitivity with low applied fields. Using this technique, we have observed periodic entry of vortices into mesoscopic Sr2 RuO4 rings. The quantized jump in the magnetic moment of the particle produced by individual vortices was measured with a resolution of 7× 10-16 emu with an applied field of 1 Oe. © 2011 American Institute of Physics.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Eguchi2011,

title = {Crystallographic and superconducting properties of the fully gapped noncentrosymmetric 5d-electron superconductors CaMSi3 (M= Ir, Pt)},

author = {G Eguchi and D C Peets and M Kriener and Y Maeno and E Nishibori and Y Kumazawa and K Banno and S Maki and H Sawa},

doi = {10.1103/PhysRevB.83.024512},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {83},

number = {2},

abstract = {We report crystallographic, specific heat, transport, and magnetic properties of the recently discovered noncentrosymmetric 5d-electron superconductors CaIrSi3 (Tc=3.6 K) and CaPtSi3 (Tc=2.3 K). The specific heat suggests that these superconductors are fully gapped. The upper critical fields are less than 1 T, consistent with limitation by conventional orbital depairing. High, non-Pauli-limited μ0Hc2 values, often taken as a key signature of novel noncentrosymmetric physics, are not observed in these materials because the high carrier masses required to suppress orbital depairing and reveal the violated Pauli limit are not present. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Jang2011186,

title = {Observation of half-height magnetization steps in Sr2RuO 4},

author = {J Jang and D G Ferguson and V Vakaryuk and R Budakian and S B Chung and P M Goldbart and Y Maeno},

doi = {10.1126/science.1193839},

year  = {2011},

date = {2011-01-01},

journal = {Science},

volume = {331},

number = {6014},

pages = {186-188},

abstract = {Spin-triplet superfluids can support exotic objects, such as half-quantum vortices characterized by the nontrivial winding of the spin structure. We present cantilever magnetometry measurements performed on mesoscopic samples of Sr2RuO4, a spin-triplet superconductor. With micrometersized annular-shaped samples, we observed transitions between integer fluxoid states as well as a regime characterized by "half-integer transitions"-steps in the magnetization with half the height of the ones we observed between integer fluxoid states. These half-height steps are consistent with the existence of half-quantum vortices in superconducting Sr 2RuO4.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kitagawa2011,

title = {Metamagnetic behavior and Kondo breakdown in heavy-fermion CeFePO},

author = {S Kitagawa and H Ikeda and Y Nakai and T Hattori and K Ishida and Y Kamihara and M Hirano and H Hosono},

doi = {10.1103/PhysRevLett.107.277002},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review Letters},

volume = {107},

number = {27},

abstract = {We report that nonmagnetic heavy-fermion (HF) iron oxypnictide CeFePO with two-dimensional XY-type anisotropy shows a metamagnetic behavior at the metamagnetic field H M4T perpendicular to the c axis and that a critical behavior is observed around H M. Although the magnetic character is entirely different from that in other Ce-based HF metamagnets, H M in these metamagnets is linearly proportional to the inverse of the effective mass, or to the temperature where the susceptib+ility shows a peak. This finding suggests that H M is a magnetic field breaking the local Kondo singlet, and the critical behavior around H M is driven by the Kondo breakdown accompanied by the Fermi-surface instability. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kii2011897,

title = {Conceptual design of a novel insertion device using bulk superconducting magnet},

author = {T Kii and R Kinjo and M A Bakr and Y W Choi and K Yoshida and S Ueda and M Takasaki and K Ishida and N Kimura and T Sonobe and K Masuda and H Ohgaki},

doi = {10.1016/j.physc.2011.05.083},

year  = {2011},

date = {2011-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {471},

number = {21-22},

pages = {897-900},

abstract = {An undulator or a wiggler with a strong magnetic field will play an important role in future synchrotron light sources, free electron lasers, and linear colliders. We proposed the bulk high critical temperature superconductor staggered array undulator (Bulk HTSC SAU) in order to generate a strong periodic field. The Bulk HTSC SAU consists of stacked bulk high-Tc superconductors (HTSs) and a solenoid magnet which is used to magnetize the bulk HTSs. A periodic magnetic field was produced and controlled using a prototype of the Bulk HTSC SAU using 11 pairs of REBaCuO bulk HTSs at 77 K. The expected performance at low temperatures around 20 K is calculated using a loop current model. © 2011 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hattori2011,

title = {59Co-NMR/nuclear-quadrupole-resonance (NQR) studies on ferromagnetic superconductor UCoGe},

author = {T Hattori and Y Ihara and K Ishida and Y Nakai and E Osaki and K Deguchi and N K Sato and I Satoh},

doi = {10.1143/JPSJS.80SA.SA007},

year  = {2011},

date = {2011-01-01},

journal = {Journal of the Physical Society of Japan},

volume = {80},

number = {SUPPL. A},

abstract = {We have performed NMR and nuclear-quadrupole-resonance (NQR) on U-based ferromagnetic superconductor UCoGe and a reference metallic compound YCoGe without 5f electrons, in order to investigate the normal and superconducting-state properties. From 59Co-NQR measurements, we give clear evidence that ferromagnetism and superconductivity coexist microscopically, both of which are ascribed to the U 5 f-electrons. In addition, direction-dependent Knight shift and nuclear spin-lattice relaxation rate measurements provide microscopic evidence that both static and dynamic susceptibilities are ferromagnetic with strong Ising anisotropy. We point out that superconductivity induced by such magnetic fluctuations prefers spin-triplet pairing state © 2011 The Physical Society of Japan.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bakr2011,

title = {Back bombardment for dispenser and lanthanum hexaboride cathodes},

author = {M Bakr and R Kinjo and Y W Choi and M Omer and K Yoshida and S Ueda and M Takasaki and K Ishida and N Kimura and T Sonobe and T Kii and K Masuda and H Ohgaki and H Zen},

doi = {10.1103/PhysRevSTAB.14.060708},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review Special Topics - Accelerators and Beams},

volume = {14},

number = {6},

abstract = {The back bombardment (BB) effect limits wide usage of thermionic rf guns. The BB effect induces not only ramping-up of a cathode's temperature and beam current, but also degradation of cavity voltage and beam energy during a macropulse. This paper presents a comparison of the BB effect for the case of dispenser tungsten-base (DC) and lanthanum hexaboride (LaB6) thermionic rf gun cathodes. For each, particle simulation codes are used to simulate the BB effect and electron beam dynamics in a thermionic rf gun cathode. A semiempirical equation is also used to investigate the stopping range and deposited heat power of BB electrons in the cathode material. A numerical simulation method is used to calculate the change of the cathode temperature and current density during a single macropulse. This is done by solving two differential equations for the rf gun cavity equivalent circuit and one-dimensional thermal diffusion equation. High electron emission and small beam size are required for generation of a high-brightness electron beam, and so in this work the emission properties of the cathode are taken into account. Simulations of the BB effect show that, for a pulse of 6μs duration, the DC cathode experiences a large change in the temperature compared with LaB 6, and a change in current density 6 times higher. Validation of the simulation results is performed using experimental data for beam current beyond the gun exit. The experimental data is well reproduced using the simulation method. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ishida2011515,

title = {NMR studies on iron-pnictide superconductors: LaFeAs(O1-xFx) and BaFe2(As1-xPx)2},

author = {K Ishida and Y Nakai and S Kitagawa and T Iye},

doi = {10.1016/j.crhy.2011.04.004},

year  = {2011},

date = {2011-01-01},

journal = {Comptes Rendus Physique},

volume = {12},

number = {5-6},

pages = {515-531},

abstract = {This review presents a summary of our NMR experiments on LaFeAs(O1-xFx) and BaFe2(As1-xPx)2. The authors introduce the key NMR experimental results which reveal their physical properties in the normal and superconducting states. From the comparison of the NMR results between the two systems, we point out that the superconducting gap structure and the relationship between superconductivity and magnetic fluctuations probed with NMR are quite different between the two systems. © 2011 Académie des sciences.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Karube2011,

title = {59Co-nuclear quadrupole resonance and nuclear magnetic resonance studies on YCoGe - Comparison between YCoGe and UCoGe},

author = {K Karube and T Hattori and Y Ihara and Y Nakai and K Ishida and N Tamura and K Deguchi and N K Sato and H Harima},

doi = {10.1143/JPSJ.80.064711},

year  = {2011},

date = {2011-01-01},

journal = {Journal of the Physical Society of Japan},

volume = {80},

number = {6},

abstract = {We have performed 59 Co-nuclear quadrupole resonance (NQR) and nuclear magnetic resonance (NMR) studies on YCoGe, which is a reference compound of ferromagnetic superconductor UCoGe, in order to investigate the magnetic properties at the Co site. Magnetic and superconducting transitions were not observed down to 0.3 K, but a conventional metallic behavior was found in YCoGe, although its crystal structure is similar to that of uCoGe. From the comparison between experimental results of two compounds, the ferromagnetism and superconductivity observed in UCoGe originate from the U-5f electrons. © 2011 The Physical Society of Japan.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kitagawa2011b,

title = {Nonmagnetic pair-breaking effect in La(Fe1-xZn x)AsO0.85 studied by As75 and La139 NMR and NQR},

author = {S Kitagawa and Y Nakai and T Iye and K Ishida and Y F Guo and Y G Shi and K Yamaura and E Takayama-Muromachi},

doi = {10.1103/PhysRevB.83.180501},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {83},

number = {18},

abstract = {As75 and La139 NMR and nuclear quadrupole resonance (NQR) studies on Zn-substituted LaFeAsO0.85 have been performed to microscopically investigate the Zn-impurity effects. Although superconductivity in LaFeAsO 0.85 disappears by 3% Zn substitution, we found that NMR/NQR spectra and NMR physical quantities in the normal state are hardly changed, indicating that the crystal structure and electronic states are not modified by Zn substitution. Our results suggest that the suppression of superconductivity by Zn substitution is not due to the change of the normal-state properties, but due to strong nonmagnetic pair-breaking effect to superconductivity. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Shu2011,

title = {Suppression of time-reversal symmetry breaking superconductivity in Pr(Os1-xRux)4Sb12 and Pr 1-yLayOs4Sb12},

author = {L Shu and W Higemoto and Y Aoki and A D Hillier and K Ohishi and K Ishida and R Kadono and A Koda and O O Bernal and D E MacLaughlin and Y Tunashima and Y Yonezawa and S Sanada and D Kikuchi and H Sato and H Sugawara and T U Ito and M B Maple},

doi = {10.1103/PhysRevB.83.100504},

year  = {2011},

date = {2011-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {83},

number = {10},

abstract = {Zero-field muon spin relaxation experiments have been carried out in the Pr(Os1-xRux)4Sb12 and Pr 1-yLayOs4Sb12 alloy systems to investigate broken time-reversal symmetry (TRS) in the superconducting state, signaled by the onset of a spontaneous static local magnetic field B s. In both alloy series Bs initially decreases linearly with solute concentration. Ru doping is considerably more efficient than La doping, with a ~50% faster initial decrease. The data suggest that broken TRS is suppressed for Ru concentration x>0.6 but persists for essentially all La concentrations. Our data support a crystal-field excitonic Cooper pairing mechanism for TRS-breaking superconductivity. © 2011 American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kriener2010,

title = {AC susceptibility study of superconducting aluminum-doped silicon carbide},

author = {M Kriener and T Muranaka and J Akimitsu and Y Maeno},

doi = {10.1016/j.physc.2009.12.009},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S602-S603},

abstract = {In 2007, type-I superconductivity in heavily boron-doped silicon carbide was discovered. The question arose, if it is possible to achieve a superconducting phase by introducing dopants different from boron. Recently, aluminum-doped silicon carbide was successfully found to superconduct by means of resistivity and DC magnetization measurements [1]. In contrast to boron-doped silicon carbide, the aluminum doped system is treated as a type-II superconductor because of the absence of an hysteresis in data measured upon decreasing and increasing temperature in finite magnetic fields. In this paper, results of a recent AC susceptibility study on aluminum-doped silicon carbide are presented. In higher applied DC magnetic fields and at low temperatures, a weak indication of supercooling with a width of a few mK is found. This supports the conclusion that aluminum-doped silicon carbide is located near to the border between type-I and type-II superconductivity, as pointed out in a recent theoretical work, too. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nakagawa2010,

title = {Superconducting properties of the Pb/Sr2RuO4/Pb proximity junction},

author = {R Nakagawa and T Nakamura and T Terashima and S Yonezawa and Y Maeno},

doi = {10.1016/j.physc.2010.01.015},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S744-S745},

abstract = {A number of experimental results have provided strong evidence for spin-triplet odd-parity superconductivity in Sr2RuO4. In order to examine this paring symmetry further, we investigated Pb/Sr 2RuO4/Pb proximity junctions which are considered to be sensitive to the parity of the superconducting wavefunction. Using the focused ion beam technique, we fabricated Pb/Sr2RuO4/Pb junctions in which the arrangement of Ru lamellae, which are needed to provide good electrical contact between Pb and Sr2RuO4, were precisely known. A sharp decrease of the critical current just below the critical temperature of Sr2RuO4 was observed, reproducing previous results, for which the arrangement of Ru lamellae was not known. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kittaka2010,

title = {Uniaxial pressure effect on the superconductivity in the Sr 3Ru2O7 region of the Sr3Ru 2O7-Sr2RuO4 eutectic system},

author = {S Kittaka and H Yaguchi and Y Maeno and R Fittipaldi and A Vecchione},

doi = {10.1016/j.physc.2009.11.038},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S728-S729},

abstract = {In the Sr3Ru2O7 region of the Sr 3Ru2O7-Sr2RuO4 eutectic system, multiple superconducting (SC) transitions are observed with onset temperatures of 1.3 and 1 K. Based on various experimental results, the SC transition at 1.3 K is attributable to thin Sr2RuO4 layers embedded in the Sr3Ru2O7 region as stacking faults. In this study, in order to clarify the origin of the SC transition at 1 K we have investigated its uniaxial pressure effect along the c axis. We revealed that, although Sr3Ru2O7 exhibits ferromagnetism under the uniaxial pressure along the c axis above 0.3 GPa, the onset temperature of the SC transition at 1 K is almost invariant or increases slightly under the uniaxial pressure up to 0.4 GPa. This result suggests that this SC transition is not strongly related to the electronic state of Sr 3Ru2O7 and it is consistent with the scenario that the 1-K transition also originates from the embedded thin Sr 2RuO4 layers whose thickness is thinner than that of the 1.3-K transition. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kambara2010,

title = {Unconventional transport characteristics of p-wave superconducting junctions in Sr2RuO4-Ru eutectic system},

author = {H Kambara and S Kashiwaya and H Yaguchi and Y Asano and Y Tanaka and Y Maeno},

doi = {10.1016/j.physc.2010.02.013},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S685-S687},

abstract = {We report on novel local transport characteristics of naturally formed p-wave superconducting junctions of Sr2RuO4-Ru eutectic system by using microfabrication technique. We observed quite anomalous voltage-current (differential resistance-current) characteristics for both I//ab and I//c directions, which are not seen in conventional Josephson junctions. The anomalous features suggest the internal degrees of freedom of the superconducting state, possibly due to chiral p-wave domain. The dc current acts as a driving force to move chiral p-wave domain walls and form larger critical current path to cause the anomalous hysteresis. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Eguchi2010,

title = {Superconducting properties of noncentrosymmetric CaIrSi3},

author = {G Eguchi and D C Peets and M Kriener and S Maki and E Nishibori and H Sawa and Y Maeno},

doi = {10.1016/j.physc.2009.11.120},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S762-S763},

abstract = {We report the temperature dependence of resistivity, DC magnetic susceptibility and heat capacity for the noncentrosymmetric superconductor CaIrSi3. The bulk superconducting transition temperature T c is about 3.0 K. The upper critical field Hc2 estimated from the H-T phase diagram is 0.44 T, yielding a superconducting coherence length: ξ(0) = 27 nm. The heat capacity exhibits a clear jump at T c indicating bulk superconductivity and is well described within the BCS framework. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yamauchi2010,

title = {Pressure induced novel-phenomena in Mott insulator Ca2RuO 4},

author = {Y Yamauchi and F Nakamura and M Sakaki and T Takemoto and T Suzuki and P L Alireza and Y Maeno},

doi = {10.1016/j.physc.2009.12.049},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S740-S741},

abstract = {In order to explore unconventional superconductivity, we have studied pressure effect on a 4d-electron Mott insulator Ca2RuO4. Pressurisation to Ca2RuO4 above 0.5 GPa transforms it from a Mott insulator to a metal with a ferromagnetic ground state. The itinerancy of the ferromagnetic state at 2 GPa is quantitatively evidenced by the magnetisation process at 2 K. Moreover, the pressure phase diagram of this system suggests the existence of a ferromagnetic quantum phase transition at ∼10 GPa. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kashiwaya2010,

title = {Fabrication and transport properties of Sr2RuO4 microdevices},

author = {S Kashiwaya and H Kambara and H Kashiwaya and T Furuta and H Yaguchi and Y Asano and Y Tanaka and Y Maeno},

doi = {10.1016/j.physc.2010.02.007},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S736-S737},

abstract = {To search for the possible existence of half quantum vortices in chiral p-wave superconductors, we fabricate Sr2RuO4-based superconducting quantum interference devices from bulk crystals using a focused ion beam process. The transport properties measured below 1.5 K show the presence of supercurrent in weak link bridges, and the switchings of the bridges to the finite voltage states against the increment of the bias current exhibit complex responses. Expected modulation of the critical current in an applied magnetic field has not been detected at present. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Takatsu20103461,

title = {Single crystal growth of the metallic triangular-lattice antiferromagnet PdCrO2},

author = {H Takatsu and Y Maeno},

doi = {10.1016/j.jcrysgro.2010.08.043},

year  = {2010},

date = {2010-01-01},

journal = {Journal of Crystal Growth},

volume = {312},

number = {23},

pages = {3461-3465},

abstract = {We report details of single crystal growth of the metallic triangular-lattice antiferromagnet PdCrO2 consisting of layers of Pd triangles and Cr triangles stacking along the c-axis. We used the NaCl flux method and obtained the crystals with the size as large as 2×3.5×0.3 mm3. We confirmed that single crystals have the delafossite structure with the R3m symmetry. The electrical resistivity along the c-axis and that in the ab plane exhibit metallic temperature dependence with the anisotropic ratio ρc/ρab of over 300 at low temperatures. The residual resistivity of as small as ρ0},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Takatsu2010b,

title = {Unconventional anomalous hall effect in the metallic triangular-lattice magnet PdCrO2},

author = {H Takatsu and S Yonezawa and S Fujimoto and Y Maeno},

doi = {10.1103/PhysRevLett.105.137201},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review Letters},

volume = {105},

number = {13},

abstract = {We experimentally reveal an unconventional anomalous Hall effect (UAHE) in a quasi-two-dimensional triangular-lattice antiferromagnet PdCrO2. Using high quality single crystals of PdCrO2, we found that the Hall resistivity ρxy deviates from the conventional behavior below T*20K, noticeably lower than TN=37.5K, at which Cr3+ (S=3/2) spins order in a 120°structure. In view of the theoretical expectation that the spin chirality cancels out in the simplest 120° spin structure, we discuss required conditions for the emergence of UAHE within Berry-phase mechanisms. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Stock2010,

title = {Neutron-scattering measurement of incommensurate short-range order in single crystals of the S=1 triangular antiferromagnet NiGa2S 4},

author = {C Stock and S Jonas and C Broholm and S Nakatsuji and Y Nambu and K Onuma and Y Maeno and J -H Chung},

doi = {10.1103/PhysRevLett.105.037402},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review Letters},

volume = {105},

number = {3},

abstract = {Neutron scattering is used to investigate spin correlations in ultrapure single crystals of the S=1 triangular lattice NiGa2S4. Despite a Curie-Weiss temperature of ΘCW=-80(2)K, static (τ>1ns) short-range (ξab=26(3)Å) incommensurate order prevails for T>1.5K. The incommensurate modulation Q0=(0.155(3),0.155(3),0), ΘCW, and the spin-wave velocity (c=4400m/s) can be accounted for by antiferromagnetic third-nearest-neighbor interactions J3=2.8(6)meV and ferromagnetic nearest-neighbor coupling J1=-0.35(9) J3. Interplane correlations are limited to nearest neighbors and weakened by an in-plane field. These observations show that the short-range ordered glassy phase that has been observed in a number of highly degenerate systems can persist near the clean limit. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kambara2010b,

title = {DC current driven critical current variation in Sr2RuO 4-Ru junction proved by local transport measurements},

author = {H Kambara and T Matsumoto and H Kashiwaya and S Kashiwaya and H Yaguchi and Y Asano and Y Tanaka and Y Maeno},

doi = {10.1143/JPSJ.79.074708},

year  = {2010},

date = {2010-01-01},

journal = {Journal of the Physical Society of Japan},

volume = {79},

number = {7},

abstract = {To search for new evidence of the chiral p-wave superconducting domain in Sr2RuO4, we investigated the unconventional local transport characteristics of a microfabricated Sr2RuO4-Ru eutectic junction. We found that the anomalous hysteresis in voltage-current characteristics [as reported in Kambara et al.: Phys. Rev. Lett. 101 (2008) 267003] is strongly affected by dc currents, but not by magnetic fields. This suggests that dc current acts as a driving force to move chiral p-wave domain walls; a domain wall trapped at a pinning potential is forced to shift to the next stable position, thereby forming a larger critical current path and resulting in the anomalous hysteresis. © 2010 The Physical Society of Japan.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hicks2010,

title = {Limits on superconductivity-related magnetization in Sr2RuO 4 and PrOs4Sb12 from scanning SQUID microscopy},

author = {C W Hicks and J R Kirtley and T M Lippman and N C Koshnick and M E Huber and Y Maeno and W M Yuhasz and M B Maple and K A Moler},

doi = {10.1103/PhysRevB.81.214501},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {81},

number = {21},

abstract = {We present scanning superconducting quantum interference device microscopy data on the superconductors Sr2RuO4 (Tc =1.5K) and PrOs4Sb12 (Tc =1.8K). In both of these materials, superconductivity-related time-reversal symmetry-breaking fields have been observed by muon spin rotation; our aim was to visualize the structure of these fields. However, in neither Sr2RuO4 nor PrOs 4Sb12 do we observe spontaneous superconductivity-related magnetization. In Sr2RuO4, many experimental results have been interpreted on the basis of a px ±i py superconducting order parameter. This order parameter is expected to give spontaneous magnetic induction at sample edges and order parameter domain walls. Supposing large domains, our data restrict domain wall and edge fields to no more than ∼0.1% and ∼0.2% of the expected magnitude, respectively. Alternatively, if the magnetization is of the expected order, the typical domain size is limited to ∼30nm for random domains or ∼500nm for periodic domains. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ishii20107055,

title = {Low-dimensional structure and magnetism of the quantum antiferromagnet Rb4Cu(MoO4)3 and the structure of Rb 4Zn(MoO4)3},

author = {R Ishii and D Gautreaux and K Onuma and Y MacHida and Y Maeno and S Nakatsuji and J Y Chan},

doi = {10.1021/ja100077v},

year  = {2010},

date = {2010-01-01},

journal = {Journal of the American Chemical Society},

volume = {132},

number = {20},

pages = {7055-7061},

abstract = {Single crystals of the quantum low-dimensional antiferromagnet Rb 4Cu(MoO4)3 and the nonmagnetic analogue Ru 4Zn(MoO4)3 have been synthesized by a flux-growth method. Detailed structural studies indicate that the Cu(II)-O network separated by a MoO4 layer has a strongly anisotropic hybridization along the a-axis, forming a quasi-one-dimensional (1-d) chain of Cu(II) S = 1/2 spins. Furthermore, our low-temperature thermodynamic measurements have revealed that a quantum paramagnetic state with Wilson ratio ∼2 remains stable down to at least 0.1 K, 100 times lower than the intrachain antiferromagnetic coupling scale. The low-temperature magnetic and thermal properties are found to be consistent with theoretical predictions made for a 1-d network of S = 1/2 spins. © 2010 American Chemical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kittaka2010b,

title = {Higher- Tc superconducting phase in Sr2 RuO 4 induced by uniaxial pressure},

author = {S Kittaka and H Taniguchi and S Yonezawa and H Yaguchi and Y Maeno},

doi = {10.1103/PhysRevB.81.180510},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {81},

number = {18},

abstract = {We have investigated uniaxial pressure effect on superconductivity of pure Sr2 RuO4, whose intrinsic superconducting transition temperature Tc is 1.5 K. It is revealed that a very low uniaxial pressure along the c axis, only 0.2 GPa, induces superconductivity with the onset Tc above 3 K. The present results indicate that pure Sr 2 RuO4 has two superconducting phases with Tc =1.5 K and with varying Tc up to 3.2 K. The latter phase exhibits unusual features and is attributable to anisotropic crystal distortions beyond the elastic limit. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Yamaguchi2010,

title = {High-field ESR and magnetization of the triangular lattice antiferromagnet NiGa2S4},

author = {H Yamaguchi and S Kimura and M Hagiwara and Y Nambu and S Nakatsuji and Y Maeno and A Matsuo and K Kindo},

doi = {10.1143/JPSJ.79.054710},

year  = {2010},

date = {2010-01-01},

journal = {Journal of the Physical Society of Japan},

volume = {79},

number = {5},

abstract = {We report the experimental and analytical results of electron spin resonance (ESR) and magnetization at high magnetic fields of up to about 68 T of the quasi two-dimensional triangular lattice antiferromagnet NiGa 2S4. From the temperature evolution of the ESR absorption linewidth, we find a distinct disturbance of the development of the spin correlation by Z2-vortices between 23 and 8.5 K. Below Tv = 8.5 K, spin-wave calculations based on a 57° spiral spin order well explain the frequency dependence of the ESR resonance fields and high-field magnetization processes for H ∥ c and H ⊥ c, although the magnetization for H ⊥ c at high fields is different from the calculated one. Furthermore, we explain the field-independent specific heat with a T2 dependence by the same spin-wave calculation, but the magnitude of specific heat is much less than the observed one. The single ion anisotropy constant D/kB = 0.8K is the same order of TV(ξ/a)-2 = 0.3-0.4K where ξ and a are the correlation length and the lattice constant of the triangular plane in NiGa2S4, respectively. The relation D/kB ≤ TV(ξ/a)-2 recently derived by Kawamura et al. [H. Kawamura et al.: J. Phys. Soc. Jpn. 79 (2010) 023701] is a necessary condition for the realization of a Z2-vortex- induced topological transition, which would be destroyed by an extremely small D ≠ 0 in a classical nearest-neighbor spin model owing to the large ξ. Accordingly, these results suggest the occurrence of a Z2-vortex- induced topological transition at Tv and indicate quantum effects beyond the descriptions based on the above classical spin models, for example, those due to quadrupolar correlations. © 2010 The Physical Society of Japan.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Stingl2010574,

title = {Anisotropy of the low-temperature basic solid state physics magnetostriction of Sr3Ru2O7},

author = {C Stingl and R S Perry and Y Maeno and P Gegenwart},

doi = {10.1002/pssb.200983034},

year  = {2010},

date = {2010-01-01},

journal = {Physica Status Solidi (B) Basic Research},

volume = {247},

number = {3},

pages = {574-576},

abstract = {Weuse high-resolution capacitive dilatometry to study the lowtemperature linear magnetostriction of the bilayer ruthenate Sr3Ru2O7 as a function of magnetic field applied perpendicular to the ruthenium-oxide planes (B k c). The relative length change ΔL(B)/L is detected either parallel or perpendicular to the c-axis close to the metamagnetic region near B=8T. In both cases, clear peaks in the coefficient λ(B) = d(ΔL/L)/dB at three subsequent metamagnetic transitions are observed. For ΔL ? c, the third transition at 8.1 T bifurcates at temperatures below 0.5 K. This is ascribed to the effect of an in-plane uniaxial pressure of about 15 bar, unavoidable in the dilatometer, which breaks the original fourfold in-plane symmetry. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Alireza2010,

title = {Evidence of superconductivity on the border of quasi-2D ferromagnetism in Ca2RuO4 at high pressure},

author = {P L Alireza and F Nakamura and S K Goh and Y Maeno and S Nakatsuji and Y T C Ko and M Sutherland and S Julian and G G Lonzarich},

doi = {10.1088/0953-8984/22/5/052202},

year  = {2010},

date = {2010-01-01},

journal = {Journal of Physics Condensed Matter},

volume = {22},

number = {5},

abstract = {The layered perovskite Ca2RuO4 is a spin-one Mott insulator at ambient pressure and exhibits metallic ferromagnetism at least up to ∼80kbar with a maximum Curie temperature of 28K. Above ∼90 and up to 140kbar, the highest pressure reached, the resistivity and ac susceptibility show pronounced downturns below ∼0.4K in applied magnetic fields of up to ∼10mT. This indicates that our specimens of Ca2RuO4 are weakly superconducting on the border of a quasi-2D ferromagnetic state. © 2010 IOP Publishing Ltd.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kitagawa2010,

title = {F-doping dependence of 75As nuclear quadrupole resonance frequency in LaFeAs(O1-xFx)},

author = {S Kitagawa and Y Nakai and T Iye and K Ishida and Y Kamihara and M Hirano and H Hosono},

doi = {10.1016/j.physc.2009.10.106},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S282-S283},

abstract = {We report the F-doping dependence of 75As nuclear quadruple resonance frequency (75νQ) in the iron-oxypnictide LaFeAs(O1-xFx) (x = 0, 0.07, 0.08, 0.11 and 0.14). It was revealed that 75νQ becomes larger with increasing x up to 0.14. From point charge calculations, we found that experimental F-doping dependence of 75νQ cannot be accounted for by the effect of surrounding ions. Therefore, the on-site charge distribution at the 75As site modified by the hybridization between As-4p and Fe-3d orbitals gives dominant contribution to 75νQ in LaFeAs(O1-xFx). © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Hattori2010,

title = {Weakly first-order behavior in ferromagnetic transition of UCoGe revealed by 59Co-NQR studies},

author = {T Hattori and K Ishida and Y Nakai and T Ohta and K Deguchi and N K Sato and I Satoh},

doi = {10.1016/j.physc.2009.10.057},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S561-S563},

abstract = {We have performed 59Co nuclear quadrupole resonance (NQR) measurements on ferromagnetic (FM) superconductor UCoGe, in which ferromagnetism occurs at TCurie ∼ 2.5 K. By measuring NQR spectrum at various temperatures, we investigated the development of local magnetic moment around TCurie, and suggest that FM transition possesses weakly first-order character. This first-order behavior is consistent with the theoretical prediction that the low temperature FM transition in itinerant magnets is generically of first-order. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nakai2010,

title = {Antiferromagnetic fluctuations in iron pnictide superconductor BaFe 2(As0.67P0.33)2 investigated by 31P NMR},

author = {Y Nakai and T Iye and S Kitagawa and K Ishida and S Kasahara and T Shibauchi and Y Matsuda and T Terashima},

doi = {10.1016/j.physc.2010.01.047},

year  = {2010},

date = {2010-01-01},

journal = {Physica C: Superconductivity and its Applications},

volume = {470},

number = {SUPPL.1},

pages = {S420-S421},

abstract = {31P NMR was performed on the normal state in the newly discovered iron pnictide superconductor BaFe2(As0.67P 0.33)2 with maximum Tc of 30 K. The Knight shift is temperature-independent while the nuclear spin-lattice relaxation rate divided by temperature (T1T)-1 exhibits a more than twofold increase on cooling. This contrasting behavior clearly indicates the development of low-lying antiferromagnetic fluctuations in BaFe2(As 0.67P0.33)2 as observed in (Ba 1-xKx)Fe2As2. The observed low-lying antiferromagnetic fluctuations may be universal in optimally doped "122" superconductors, in contrast to "1111" superconductors. © 2009 Elsevier B.V. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Klintberg2010,

title = {Chemical pressure and physical pressure in BaFe2(As 1-xPx)2},

author = {L E Klintberg and S K Goh and S Kasahara and Y Nakai and K Ishida and M Sutherland and T Shibauchi and Y Matsuda and T Terashima},

doi = {10.1143/JPSJ.79.123706},

year  = {2010},

date = {2010-01-01},

journal = {Journal of the Physical Society of Japan},

volume = {79},

number = {12},

abstract = {Measurements of the superconducting transition temperature, Tc, under hydrostatic pressure via bulk AC susceptibility were carried out on several concentrations of phosphorous substitution in BaFe2-(As 1-xPx)2. The pressure dependence of unsubstituted BaFe2As2, phosphorous concentration dependence of BaFe2(As1-xPx)2, as well as the pressure dependence of BaFe2(As1-xP x)2 all point towards an identical maximum Tc of 31 K. This demonstrates that phosphorous substitution and physical pressure result in similar superconducting phase diagrams, and that phosphorous substitution does not induce substantial impurity scattering. © 2010 The Physical Society of Japan.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ihara2010,

title = {Anisotropic magnetic fluctuations in the ferromagnetic superconductor UCoGe studied by direction-dependent Co59 NMR measurements},

author = {Y Ihara and T Hattori and K Ishida and Y Nakai and E Osaki and K Deguchi and N K Sato and I Satoh},

doi = {10.1103/PhysRevLett.105.206403},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review Letters},

volume = {105},

number = {20},

abstract = {We have carried out direction-dependent Co59 NMR experiments on a single crystal sample of the ferromagnetic superconductor UCoGe in order to study the magnetic properties in the normal state. The Knight-shift and nuclear spin-lattice relaxation rate measurements provide microscopic evidence that both static and dynamic susceptibilities are ferromagnetic with strong Ising anisotropy. We discuss that superconductivity induced by these magnetic fluctuations prefers spin-triplet pairing state. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Goh2010,

title = {Anisotropic superconducting properties of optimally doped BaFe 2(As0.65P0.35)2 under pressure},

author = {S K Goh and Y Nakai and K Ishida and L E Klintberg and Y Ihara and S Kasahara and T Shibauchi and Y Matsuda and T Terashima},

doi = {10.1103/PhysRevB.82.094502},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {82},

number = {9},

abstract = {Magnetic measurements on optimally doped single crystals of BaFe 2 (As1-xPx)2 (x≈0.35) with magnetic fields applied along different crystallographic axes were performed under pressure, enabling the pressure evolution of coherence lengths and the anisotropy factor to be followed. Despite a decrease in the superconducting critical temperature, our studies reveal that the superconducting properties become more anisotropic under pressure. With appropriate scaling, we directly compare these properties with the values obtained for BaFe2 (As 1-xPx)2 as a function of phosphorus content. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nakai2010b,

title = {Unconventional superconductivity and antiferromagnetic quantum critical behavior in the isovalent-doped BaFe2(As1-xP x)2},

author = {Y Nakai and T Iye and S Kitagawa and K Ishida and H Ikeda and S Kasahara and H Shishido and T Shibauchi and Y Matsuda and T Terashima},

doi = {10.1103/PhysRevLett.105.107003},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review Letters},

volume = {105},

number = {10},

abstract = {Spin dynamics evolution of BaFe2(As1-xP x)2 was probed as a function of P concentration via P31 NMR. Our NMR study reveals that two-dimensional antiferromagnetic (AF) fluctuations are notably enhanced with little change in static susceptibility on approaching the AF phase from the superconducting dome. Moreover, the magnetically ordered temperature θ deduced from the relaxation rate vanishes at optimal doping. These results provide clear-cut evidence for a quantum-critical point, suggesting that the AF fluctuations associated with the quantum-critical point play a central role in the high-Tc superconductivity.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Kitagawa2010b,

title = {Stripe antiferromagnetic correlations in LaFeAsO1-x Fx probed by A 75 s NMR},

author = {S Kitagawa and Y Nakai and T Iye and K Ishida and Y Kamihara and M Hirano and H Hosono},

doi = {10.1103/PhysRevB.81.212502},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {81},

number = {21},

abstract = {The anisotropy of the nuclear spin-lattice relaxation rate 1/T1 of A 75 As was investigated in the iron pnictide LaFeAs (O 1-xFx) (x=0.07, 0.11, and 0.14) as well as LaFeAsO. While the temperature dependence of the normal-state 1/T1T in the superconducting (SC) x=0.07 is different from that in the SC x=0.11, their anisotropy of 1/T1, R≡(1/T1)H∥ab/(1/ T1)H∥c in the normal state is almost the same (∼1.5). The observed anisotropy is ascribable to the presence of the local stripe correlations with Q= (π,0) or (0,π). In contrast, 1/ T1 is isotropic and R is approximately 1 in the overdoped x=0.14 sample, where superconductivity is almost suppressed. These results suggest that the presence of the local stripe correlations originating from the nesting between hole and electron Fermi surfaces is linked to high- Tc superconductivity in iron pnictides. © 2010 The American Physical Society.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Ohta2010,

title = {Microscopic coexistence of ferromagnetism and superconductivity in single-crystal UCoGe},

author = {T Ohta and T Hattori and K Ishida and Y Nakai and E Osaki and K Deguchi and N K Sato and I Satoh},

doi = {10.1143/JPSJ.79.023707},

year  = {2010},

date = {2010-01-01},

journal = {Journal of the Physical Society of Japan},

volume = {79},

number = {2},

abstract = {Unambiguous evidence for the microscopic coexistence of ferromagnetism and superconductivity in UCoGe (TCurie ∼ 2:5K and TSC ∼ 0:6 K) is reported from 59Co nuclear quadrupole resonance (NQR). The 59Co-NQR signal below 1K indicates ferromagnetism throughout the sample volume, while the nuclear spin-lattice relaxation rate 1/T1 in the ferromagnetic (FM) phase decreases below TSC due to the opening of the superconducting (SC) gap. The SC state is found to be inhomogeneous, suggestive of a self-induced vortex state, potentially realizable in a FM superconductor. In addition, the 59Co-NQR spectrum around TCurie shows that the FM transition in UCoGe possesses a first-order character, which is consistent with the theoretical prediction that the low-temperature FM transition in itinerant magnets is generically of first-order. © 2010 The Physical Society of Japan.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Nakai2010c,

title = {Erratum: Systematic 75As NMR study of the dependence of low-lying excitations on F doping in the iron oxypnictide LaFeAs O1-x Fx(Physical Review B (2009) 79 (212506))},

author = {Y Nakai and S Kitagawa and K Ishida and Y Kamihara and M Hirano and H Hosono},

doi = {10.1103/PhysRevB.81.019902},

year  = {2010},

date = {2010-01-01},

journal = {Physical Review B - Condensed Matter and Materials Physics},

volume = {81},

number = {1},

keywords = {},

pubstate = {published},

tppubtype = {article}

}