Faculty
Assistant professor
Room 140
+81 (0)75 753 3752
kitagHelloUglyBot!awa.shuHelloUglyBot!nsaku.8HelloUglyBot!u@kyoto-u.ac.jp
my publications in the group follow:
2022
60.
K Kinjo, H Fujibayashi, G Nakamine, S Kitagawa, K Ishida, Y Tokunaga, H Sakai, S Kambe, A Nakamura, Y Shimizu, Y Homma, D Li, F Honda, D Aoki
Drastic change in magnetic anisotropy of UTe2 under pressure revealed by 125Te -NMR Journal Article
In: Physical Review B, vol. 105, iss. 14, pp. L140502, 2022.
@article{K.Kinjo_PRB_2022,
title = {Drastic change in magnetic anisotropy of UTe2 under pressure revealed by 125Te -NMR},
author = {K Kinjo and H Fujibayashi and G Nakamine and S Kitagawa and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and D Aoki},
url = {https://arxiv.org/abs/2203.12934},
doi = {10.1103/PhysRevB.105.L140502},
year = {2022},
date = {2022-04-06},
urldate = {2022-04-06},
journal = {Physical Review B},
volume = {105},
issue = {14},
pages = {L140502},
abstract = {To investigate the normal-state magnetic properties of UTe2 under pressure, we perform 125Te nuclear magnetic resonance (NMR) measurements up to 2 GPa. Below 1.2 GPa, the b-axis NMR Knight shift shows a broad maximum at the so-called T_chimax on cooling, which is consistent with the magnetization measurement under pressure. T_chimax decreases with increasing pressure and disappears at the critical pressure Pc = 1.7 GPa, above which superconductivity is destroyed. This tendency is also observed in the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1. At low pressures, 1/T1 shows a conventional Fermi-liquid behavior (1/T1T = constant) at low temperatures, indicating the formation of the heavy-fermion state. Above Pc, 1/T1T follows a 1/T behavior without any crossover to the heavy-fermion state down to the lowest temperature (~3 K). In addition, the NMR signals disappear below 3 K, due to the influence of the magnetically ordered moments. From the pressure dependence of the T_chimax and Knight shift, it was found that the Fermi surface character is abruptly changed at Pc, and that superconductivity is observed only in the heavy-fermion state.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
To investigate the normal-state magnetic properties of UTe2 under pressure, we perform 125Te nuclear magnetic resonance (NMR) measurements up to 2 GPa. Below 1.2 GPa, the b-axis NMR Knight shift shows a broad maximum at the so-called T_chimax on cooling, which is consistent with the magnetization measurement under pressure. T_chimax decreases with increasing pressure and disappears at the critical pressure Pc = 1.7 GPa, above which superconductivity is destroyed. This tendency is also observed in the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1. At low pressures, 1/T1 shows a conventional Fermi-liquid behavior (1/T1T = constant) at low temperatures, indicating the formation of the heavy-fermion state. Above Pc, 1/T1T follows a 1/T behavior without any crossover to the heavy-fermion state down to the lowest temperature (~3 K). In addition, the NMR signals disappear below 3 K, due to the influence of the magnetically ordered moments. From the pressure dependence of the T_chimax and Knight shift, it was found that the Fermi surface character is abruptly changed at Pc, and that superconductivity is observed only in the heavy-fermion state.
59.
H Fujibayashi, G Nakamine, K Kinjo, S Kitagawa, K Ishida, Y Tokunaga, H Sakai, S Kambe, A Nakamura, Y Shimizu, Y Homma, D Li, F Honda, D Aoki
Superconducting Order Parameter in UTe2 Determined by Knight Shift Measurement Journal Article
In: Journal of the Physical Society of Japan, vol. 91, no. 04, pp. 043705, 2022.
@article{H.Fujibayashi_JPSJ_2022,
title = {Superconducting Order Parameter in UTe2 Determined by Knight Shift Measurement},
author = {H Fujibayashi and G Nakamine and K Kinjo and S Kitagawa and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and D Aoki},
url = {https://doi.org/10.7566/JPSJ.91.043705
https://arxiv.org/abs/2203.08598},
doi = {10.7566/JPSJ.91.043705},
year = {2022},
date = {2022-03-11},
urldate = {2022-03-11},
journal = {Journal of the Physical Society of Japan},
volume = {91},
number = {04},
pages = {043705},
abstract = {This study investigates the spin susceptibility in U-based superconductor UTe2 in the superconducting (SC) state by using Knight shift measurements for a magnetic field H along the a axis, which is the magnetic easy axis of UTe2.
Although a tiny anomaly ascribed to the SC diamagnetic effect was observed just below the SC transition temperature Tc, the a-axis Knight shift in the SC state shows no significant decrease, following the extrapolation from the normal-state temperature dependence.
This indicates that the spin susceptibility is nearly unchanged below Tc.
Considering the previous Knight shift results for H∥b and H∥c, the dominant SC state is determined to be B3u in the spin-triplet pairing, which is consistent with the spin anisotropy in the normal state.
The present result shows that UTe2 is a spin-triplet superconductor with spin degrees of freedom.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
This study investigates the spin susceptibility in U-based superconductor UTe2 in the superconducting (SC) state by using Knight shift measurements for a magnetic field H along the a axis, which is the magnetic easy axis of UTe2.
Although a tiny anomaly ascribed to the SC diamagnetic effect was observed just below the SC transition temperature Tc, the a-axis Knight shift in the SC state shows no significant decrease, following the extrapolation from the normal-state temperature dependence.
This indicates that the spin susceptibility is nearly unchanged below Tc.
Considering the previous Knight shift results for H∥b and H∥c, the dominant SC state is determined to be B3u in the spin-triplet pairing, which is consistent with the spin anisotropy in the normal state.
The present result shows that UTe2 is a spin-triplet superconductor with spin degrees of freedom.
Although a tiny anomaly ascribed to the SC diamagnetic effect was observed just below the SC transition temperature Tc, the a-axis Knight shift in the SC state shows no significant decrease, following the extrapolation from the normal-state temperature dependence.
This indicates that the spin susceptibility is nearly unchanged below Tc.
Considering the previous Knight shift results for H∥b and H∥c, the dominant SC state is determined to be B3u in the spin-triplet pairing, which is consistent with the spin anisotropy in the normal state.
The present result shows that UTe2 is a spin-triplet superconductor with spin degrees of freedom.
58.
S Kitagawa, M Kibune, K Kinjo, M Manago, T Taniguchi, K Ishida, M Brando, E Hassinger, C Geibel, S Khim
Two-Dimensional XY-Type Magnetic Properties of Locally Noncentrosymmetric Superconductor CeRh2As2 Journal Article
In: Journal of the Physical Society of Japan, vol. 91, no. 04, pp. 043702, 2022.
@article{S.Kitagawa_JPSJ_2021,
title = {Two-Dimensional XY-Type Magnetic Properties of Locally Noncentrosymmetric Superconductor CeRh2As2},
author = {S Kitagawa and M Kibune and K Kinjo and M Manago and T Taniguchi and K Ishida and M Brando and E Hassinger and C Geibel and S Khim},
url = {https://doi.org/10.7566/JPSJ.91.043702
https://arxiv.org/abs/2203.03184},
doi = {10.7566/JPSJ.91.043702},
year = {2022},
date = {2022-03-04},
journal = {Journal of the Physical Society of Japan},
volume = {91},
number = {04},
pages = {043702},
abstract = {We performed 75As-NMR measurements to investigate the normal-state magnetic properties of CeRh2As2, a recently-discovered heavy-fermion superconductor.
The magnitude and temperature dependence of the Knight shift at the As(2) site indicate easy-plane-type magnetic anisotropy in CeRh2As2.
With regard to spin fluctuations, the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1 arising from the 4f electrons decreases from high-temperature constant behavior on cooling at ∼ 40~K, which is typical behavior of heavy-fermion systems.
In addition, 1/T1 becomes constant at low temperatures, suggesting spatially two-dimensional antiferromagnetic fluctuations. Two-dimensional magnetic correlations in the real space are quite rare among heavy-fermion superconductors, and they may be a key factor in the unique superconducting multi-phase in CeRh2As2.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We performed 75As-NMR measurements to investigate the normal-state magnetic properties of CeRh2As2, a recently-discovered heavy-fermion superconductor.
The magnitude and temperature dependence of the Knight shift at the As(2) site indicate easy-plane-type magnetic anisotropy in CeRh2As2.
With regard to spin fluctuations, the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1 arising from the 4f electrons decreases from high-temperature constant behavior on cooling at ∼ 40~K, which is typical behavior of heavy-fermion systems.
In addition, 1/T1 becomes constant at low temperatures, suggesting spatially two-dimensional antiferromagnetic fluctuations. Two-dimensional magnetic correlations in the real space are quite rare among heavy-fermion superconductors, and they may be a key factor in the unique superconducting multi-phase in CeRh2As2.
The magnitude and temperature dependence of the Knight shift at the As(2) site indicate easy-plane-type magnetic anisotropy in CeRh2As2.
With regard to spin fluctuations, the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1 arising from the 4f electrons decreases from high-temperature constant behavior on cooling at ∼ 40~K, which is typical behavior of heavy-fermion systems.
In addition, 1/T1 becomes constant at low temperatures, suggesting spatially two-dimensional antiferromagnetic fluctuations. Two-dimensional magnetic correlations in the real space are quite rare among heavy-fermion superconductors, and they may be a key factor in the unique superconducting multi-phase in CeRh2As2.
57.
M Kibune, S Kitagawa, K Kinjo, S Ogata, M Manago, T Taniguchi, K Ishida, M Brando, E Hassinger, H Rosner, C Geibel, S Khim
Observation of Antiferromagnetic Order as Odd-Parity Multipoles inside the Superconducting Phase in CeRh2As2 Journal Article
In: Physical Review Letters, vol. 128, no. 05, pp. 057002, 2022.
@article{S.Kitagawa_PRL_2022,
title = {Observation of Antiferromagnetic Order as Odd-Parity Multipoles inside the Superconducting Phase in CeRh2As2},
author = {M Kibune and S Kitagawa and K Kinjo and S Ogata and M Manago and T Taniguchi and K Ishida and M Brando and E Hassinger and H Rosner and C Geibel and S Khim},
url = {https://arxiv.org/abs/2112.07081},
doi = {10.1103/PhysRevLett.128.057002},
year = {2022},
date = {2022-02-03},
urldate = {2022-02-03},
journal = {Physical Review Letters},
volume = {128},
number = {05},
pages = {057002},
abstract = {Spatial inversion symmetry in crystal structures is closely related to the superconducting (SC) and magnetic properties of materials. Recently, several theoretical proposals that predict various interesting phenomena caused by the breaking of the local inversion symmetry have been presented. However, experimental validation has not yet progressed owing to the lack of model materials. Here we present evidence for antiferromagnetic (AFM) order in CeRh2As2 (SC transition temperature TSC ∼ 0.37 K ), wherein the Ce site breaks the local inversion symmetry. The evidence is based on the observation of different extents of broadening of the nuclear quadrupole resonance spectrum at two crystallographically inequivalent As sites. This AFM ordering breaks the inversion symmetry of this system, resulting in the activation of an odd-parity magnetic multipole. Moreover, the onset of antiferromagnetism TN within an SC phase, with TN < TSC , is quite unusual in systems wherein superconductivity coexists or competes with magnetism. Our observations show that CeRh2As2 is a promising system to study how the absence of local inversion symmetry induces or influences unconventional magnetic and SC states, as well as their interaction.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Spatial inversion symmetry in crystal structures is closely related to the superconducting (SC) and magnetic properties of materials. Recently, several theoretical proposals that predict various interesting phenomena caused by the breaking of the local inversion symmetry have been presented. However, experimental validation has not yet progressed owing to the lack of model materials. Here we present evidence for antiferromagnetic (AFM) order in CeRh2As2 (SC transition temperature TSC ∼ 0.37 K ), wherein the Ce site breaks the local inversion symmetry. The evidence is based on the observation of different extents of broadening of the nuclear quadrupole resonance spectrum at two crystallographically inequivalent As sites. This AFM ordering breaks the inversion symmetry of this system, resulting in the activation of an odd-parity magnetic multipole. Moreover, the onset of antiferromagnetism TN within an SC phase, with TN < TSC , is quite unusual in systems wherein superconductivity coexists or competes with magnetism. Our observations show that CeRh2As2 is a promising system to study how the absence of local inversion symmetry induces or influences unconventional magnetic and SC states, as well as their interaction.
56.
Y Tokunaga, H Sakai, S Kambe, Y Haga, Y Tokiwa, P Opletal, H Fujibayashi, K Kinjo, S Kitagawa, K Ishida, A Nakamura, Y Shimizu, Y Homma, D Li, F Honda, D Aoki
Slow Electronic Dynamics in the Paramagnetic State of UTe2 Journal Article
In: Journal of the Physical Society of Japan, vol. 91, iss. 02, pp. 023707, 2022.
@article{Y.Tokunaga_JPSJ_2022,
title = {Slow Electronic Dynamics in the Paramagnetic State of UTe2},
author = {Y Tokunaga and H Sakai and S Kambe and Y Haga and Y Tokiwa and P Opletal and H Fujibayashi and K Kinjo and S Kitagawa and K Ishida and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and D Aoki},
url = {https://arxiv.org/abs/2201.07455},
doi = {10.7566/JPSJ.91.023707},
year = {2022},
date = {2022-01-27},
urldate = {2022-01-27},
journal = {Journal of the Physical Society of Japan},
volume = {91},
issue = {02},
pages = {023707},
abstract = {125Te NMR experiments in field (H) applied along the easy magnetization axis (the a-axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe2. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 30–40 K, where the spin susceptibility along the hard magnetization axis (the b-axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in H || a. We suggest that UTe2 would be located on the paramagnetic side near an electronic phase boundary, where either magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
125Te NMR experiments in field (H) applied along the easy magnetization axis (the a-axis) revealed slow electronic dynamics developing in the paramagnetic state of UTe2. The observed slow fluctuations are concerned with a successive growth of long-range electronic correlations below 30–40 K, where the spin susceptibility along the hard magnetization axis (the b-axis) shows a broad maximum. The experiments also imply that tiny amounts of disorder or defects locally disturb the long-range electronic correlations and develop an inhomogeneous electronic state at low temperatures, leading to a low temperature upturn observed in the bulk-susceptibility in H || a. We suggest that UTe2 would be located on the paramagnetic side near an electronic phase boundary, where either magnetic or Fermi-surface instability would be the origin of the characteristic fluctuations.
55.
Y Sato, S Suetsugu, T Tominaga, Y Kasahara, S Kasahara, T Kobayashi, S Kitagawa, K Ishida, R Peters, T Shibauchi, A H Nevidomskyy, L Qian, J M Moya, E Morosan, Y Matsuda
Charge neutral fermions and magnetic field driven instability in insulating YbIr3Si7 Journal Article
In: Nature Communications, vol. 13, pp. 394, 2022.
@article{Y.Sato_NComm_2022,
title = {Charge neutral fermions and magnetic field driven instability in insulating YbIr3Si7},
author = {Y Sato and S Suetsugu and T Tominaga and Y Kasahara and S Kasahara and T Kobayashi and S Kitagawa and K Ishida and R Peters and T Shibauchi and A H Nevidomskyy and L Qian and J M Moya and E Morosan and Y Matsuda},
url = {https://arxiv.org/abs/2103.13718},
doi = {10.1038/s41467-021-27541-9},
year = {2022},
date = {2022-01-19},
urldate = {2022-01-19},
journal = {Nature Communications},
volume = {13},
pages = {394},
abstract = {Kondo lattice materials, where localized magnetic moments couple to itinerant electrons, provide a very rich backdrop for strong electron correlations. They are known to realize many exotic phenomena, with a dramatic example being recent observations of quantum oscillations and metallic thermal conduction in insulators, implying the emergence of enigmatic charge-neutral fermions. Here, we show that thermal conductivity and specific heat measurements in insulating YbIr3Si7 reveal emergent neutral excitations, whose properties are sensitively changed by a field-driven transition between two antiferromagnetic phases. In the low-field phase, a significant violation of the Wiedemann-Franz law demonstrates that YbIr3Si7 is a charge insulator but a thermal metal. In the high-field phase, thermal conductivity exhibits a sharp drop below 300 mK, indicating a transition from a thermal metal into an insulator/semimetal driven by the magnetic transition. These results suggest that spin degrees of freedom directly couple to the neutral fermions, whose emergent Fermi surface undergoes a field-driven instability at low temperatures.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Kondo lattice materials, where localized magnetic moments couple to itinerant electrons, provide a very rich backdrop for strong electron correlations. They are known to realize many exotic phenomena, with a dramatic example being recent observations of quantum oscillations and metallic thermal conduction in insulators, implying the emergence of enigmatic charge-neutral fermions. Here, we show that thermal conductivity and specific heat measurements in insulating YbIr3Si7 reveal emergent neutral excitations, whose properties are sensitively changed by a field-driven transition between two antiferromagnetic phases. In the low-field phase, a significant violation of the Wiedemann-Franz law demonstrates that YbIr3Si7 is a charge insulator but a thermal metal. In the high-field phase, thermal conductivity exhibits a sharp drop below 300 mK, indicating a transition from a thermal metal into an insulator/semimetal driven by the magnetic transition. These results suggest that spin degrees of freedom directly couple to the neutral fermions, whose emergent Fermi surface undergoes a field-driven instability at low temperatures.
2021
54.
K Ishida, S Matsuzaki, M Manago, T Hattori, S Kitagawa, M Hirata, T Sasaki, D Aoki
Pairing interaction in superconducting UCoGe tunable by magnetic field Journal Article
In: Physical Review B, vol. 104, no. 14, pp. 144505, 2021.
@article{K.Ishida_PRB_2021,
title = {Pairing interaction in superconducting UCoGe tunable by magnetic field},
author = {K Ishida and S Matsuzaki and M Manago and T Hattori and S Kitagawa and M Hirata and T Sasaki and D Aoki},
url = {https://arxiv.org/abs/2109.14426},
doi = {10.1103/PhysRevB.104.144505},
year = {2021},
date = {2021-10-18},
journal = {Physical Review B},
volume = {104},
number = {14},
pages = {144505},
abstract = {The mechanism of unconventional superconductivity, such as high-temperature-cuprate, Fe-based, and heavy-fermion superconductors, has been studied as a central issue in condensed-matter physics. Spin fluctuations, instead of phonons, are considered to be responsible for the formation of Cooper pairs, and many efforts have been made to confirm this mechanism experimentally. Although a qualitative consensus seems to have been obtained, experimental confirmation has not yet been achieved. This is owing to a lack of the quantitative comparison between theory and experiments. Here, we show a semiquantitative comparison between the superconducting-transition temperature ( T SC ) and spin fluctuations derived from the NMR experiment on the ferromagnetic (FM) superconductor UCoGe in which the FM fluctuations and superconductivity are tunable by external fields. The enhancement and abrupt suppression of T SC by applied fields, as well as the pressure variation of T SC around the FM criticality are well understood by the change in the FM fluctuations on the basis of the single-band spin-triplet theoretical formalism. The present comparisons strongly support the theoretical formalism of spin-fluctuation-mediated superconductivity, particularly in UCoGe.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The mechanism of unconventional superconductivity, such as high-temperature-cuprate, Fe-based, and heavy-fermion superconductors, has been studied as a central issue in condensed-matter physics. Spin fluctuations, instead of phonons, are considered to be responsible for the formation of Cooper pairs, and many efforts have been made to confirm this mechanism experimentally. Although a qualitative consensus seems to have been obtained, experimental confirmation has not yet been achieved. This is owing to a lack of the quantitative comparison between theory and experiments. Here, we show a semiquantitative comparison between the superconducting-transition temperature ( T SC ) and spin fluctuations derived from the NMR experiment on the ferromagnetic (FM) superconductor UCoGe in which the FM fluctuations and superconductivity are tunable by external fields. The enhancement and abrupt suppression of T SC by applied fields, as well as the pressure variation of T SC around the FM criticality are well understood by the change in the FM fluctuations on the basis of the single-band spin-triplet theoretical formalism. The present comparisons strongly support the theoretical formalism of spin-fluctuation-mediated superconductivity, particularly in UCoGe.
53.
S Kitagawa, K Ishida, A Ikeda, M Kawaguchi, S Yonezawa, Y Maeno
Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb2 under pressure Journal Article
In: Physical Review B, vol. 104, no. 6, pp. L060504, 2021.
@article{S.Kitagawa_PRB_2021,
title = {Peak in the superconducting transition temperature of the nonmagnetic topological line-nodal material CaSb_{2} under pressure},
author = {S Kitagawa and K Ishida and A Ikeda and M Kawaguchi and S Yonezawa and Y Maeno},
url = {https://arxiv.org/abs/2108.08992},
doi = {10.1103/PhysRevB.104.L060504},
year = {2021},
date = {2021-08-17},
journal = {Physical Review B},
volume = {104},
number = {6},
pages = {L060504},
abstract = {Investigating the pressure dependence of the superconducting (SC) transition temperature Tc is crucial for understanding the SC mechanism.
Herein, we report on the pressure dependence of Tc in the nonmagnetic topological line-nodal material CaSb2 based on measurements of electric resistance and alternating current magnetic susceptibility.
Tc initially increases with increasing pressure and peaks at ~ 3.1 GPa. With a further increase in pressure, Tc decreases and finally becomes undetectable at 5.9 GPa.
Because no signs of phase transition or Lifshitz transition are observed in the normal state, the peculiar peak structure of Tc suggests that CaSb2 has an unconventional SC character.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Investigating the pressure dependence of the superconducting (SC) transition temperature Tc is crucial for understanding the SC mechanism.
Herein, we report on the pressure dependence of Tc in the nonmagnetic topological line-nodal material CaSb2 based on measurements of electric resistance and alternating current magnetic susceptibility.
Tc initially increases with increasing pressure and peaks at ~ 3.1 GPa. With a further increase in pressure, Tc decreases and finally becomes undetectable at 5.9 GPa.
Because no signs of phase transition or Lifshitz transition are observed in the normal state, the peculiar peak structure of Tc suggests that CaSb2 has an unconventional SC character.
Herein, we report on the pressure dependence of Tc in the nonmagnetic topological line-nodal material CaSb2 based on measurements of electric resistance and alternating current magnetic susceptibility.
Tc initially increases with increasing pressure and peaks at ~ 3.1 GPa. With a further increase in pressure, Tc decreases and finally becomes undetectable at 5.9 GPa.
Because no signs of phase transition or Lifshitz transition are observed in the normal state, the peculiar peak structure of Tc suggests that CaSb2 has an unconventional SC character.
52.
H Takahashi, S Kitagawa, K Ishida, M Kawaguchi, A Ikeda, S Yonezawa, Y Maeno
S-Wave Superconductivity in the Dirac Line-Nodal Material CaSb2 Journal Article
In: Journal of the Physical Society of Japan, vol. 90, no. 073702, pp. 5, 2021.
@article{H.Takahashi_JPSJ_2021,
title = {S-Wave Superconductivity in the Dirac Line-Nodal Material CaSb2},
author = {H Takahashi and S Kitagawa and K Ishida and M Kawaguchi and A Ikeda and S Yonezawa and Y Maeno},
url = {https://arxiv.org/abs/2105.13614},
doi = {10.7566/JPSJ.90.073702},
year = {2021},
date = {2021-06-11},
journal = {Journal of the Physical Society of Japan},
volume = {90},
number = {073702},
pages = {5},
abstract = {We performed 121/123Sb-nuclear quadrupole resonance (NQR) measurements on the superconducting (SC) line-nodal material CaSb2 in order to investigate electronic properties in the normal and SC states from a microscopic point of view. In the normal state, the nuclear spin–lattice relaxation rate 1/T1 for the Sb(1) site, which is responsible for the line-nodal parts, is approximately proportional to temperature, indicating the conventional Fermi liquid state. From comparison with band structure calculations, it is considered that the NQR properties related to the line-nodal character are hidden because the conventional behavior originating from Fermi-surface parts away from the nodes is dominant. In the SC state, a clear coherence peak just below the transition temperature and an exponential decrease at lower temperatures were observed in 1/T1. These results strongly suggest that conventional s-wave superconductivity with a full gap is realized in CaSb2.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
We performed 121/123Sb-nuclear quadrupole resonance (NQR) measurements on the superconducting (SC) line-nodal material CaSb2 in order to investigate electronic properties in the normal and SC states from a microscopic point of view. In the normal state, the nuclear spin–lattice relaxation rate 1/T1 for the Sb(1) site, which is responsible for the line-nodal parts, is approximately proportional to temperature, indicating the conventional Fermi liquid state. From comparison with band structure calculations, it is considered that the NQR properties related to the line-nodal character are hidden because the conventional behavior originating from Fermi-surface parts away from the nodes is dominant. In the SC state, a clear coherence peak just below the transition temperature and an exponential decrease at lower temperatures were observed in 1/T1. These results strongly suggest that conventional s-wave superconductivity with a full gap is realized in CaSb2.
51.
G Nakamine, K Kinjo, S Kitagawa, K Ishida, Y Tokunaga, H Sakai, S Kambe, A Nakamura, Y Shimizu, Y Homma, D Li, F Honda, D Aoki
Inhomogeneous Superconducting State Probed by 125Te NMR on UTe2 Journal Article
In: Journal of the Physical Society of Japan, vol. 90, no. 064709, pp. 7, 2021.
@article{G.Nakamine_JPSJ_2021,
title = {Inhomogeneous Superconducting State Probed by 125Te NMR on UTe2},
author = {G Nakamine and K Kinjo and S Kitagawa and K Ishida and Y Tokunaga and H Sakai and S Kambe and A Nakamura and Y Shimizu and Y Homma and D Li and F Honda and D Aoki},
url = {https://arxiv.org/abs/2105.11823},
doi = {10.7566/JPSJ.90.064709},
year = {2021},
date = {2021-05-25},
journal = {Journal of the Physical Society of Japan},
volume = {90},
number = {064709},
pages = {7},
abstract = {UTe2 is a recently discovered promising candidate for a spin-triplet superconductor. In contrast to conventional spin-singlet superconductivity, spin-triplet superconductivity possesses spin and angular momentum degrees of freedom. To detect these degrees of freedom and obtain the solid evidence of spin-triplet superconductivity in UTe2, we have performed 125Te-NMR measurements, which are sensitive to the local spin susceptibility at a nuclear site. We previously reported that the shoulder signal appears in NMR spectra below the superconducting (SC) transition temperature Tc in H || b, and a slight decrease in the Knight shift along the b and c axes (Kb and Kc, respectively) below Tc at a low magnetic field H. Although the decrease in Kc vanished above 5.5 T, the decrease in Kb was independent of H up to 6.5 T. To clarify the origin of the shoulder signal and the trace of the decrease in Kb, we compared the 125Te-NMR spectra obtained when H || b and H || c and measured the 125Te-NMR spectra for H || b up to 14.5 T. The intensity of the shoulder signal observed for H || b has a maximum at ∼6 T and vanishes above 10 T, although the superconductivity is confirmed by the χAC measurements, which can survive up to 14.5 T (maximum H in the present measurement). Moreover, the decrease in Kb in the SC state starts to be small around 7 T and almost zero at 12.5 T. This indicates that the SC spin state gradually changes with the application of H. Meanwhile, in H || c, an unexpected broadening without the shoulder signals was observed below Tc at 1 T, and this broadening was quickly suppressed with increasing H. We construct the H–T phase diagram for H || b and H || c based on the NMR measurements and discuss possible SC states with the theoretical consideration. We suggest that the inhomogeneous SC state characterized by the broadening of the NMR spectrum originates from the spin degrees of freedom.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
UTe2 is a recently discovered promising candidate for a spin-triplet superconductor. In contrast to conventional spin-singlet superconductivity, spin-triplet superconductivity possesses spin and angular momentum degrees of freedom. To detect these degrees of freedom and obtain the solid evidence of spin-triplet superconductivity in UTe2, we have performed 125Te-NMR measurements, which are sensitive to the local spin susceptibility at a nuclear site. We previously reported that the shoulder signal appears in NMR spectra below the superconducting (SC) transition temperature Tc in H || b, and a slight decrease in the Knight shift along the b and c axes (Kb and Kc, respectively) below Tc at a low magnetic field H. Although the decrease in Kc vanished above 5.5 T, the decrease in Kb was independent of H up to 6.5 T. To clarify the origin of the shoulder signal and the trace of the decrease in Kb, we compared the 125Te-NMR spectra obtained when H || b and H || c and measured the 125Te-NMR spectra for H || b up to 14.5 T. The intensity of the shoulder signal observed for H || b has a maximum at ∼6 T and vanishes above 10 T, although the superconductivity is confirmed by the χAC measurements, which can survive up to 14.5 T (maximum H in the present measurement). Moreover, the decrease in Kb in the SC state starts to be small around 7 T and almost zero at 12.5 T. This indicates that the SC spin state gradually changes with the application of H. Meanwhile, in H || c, an unexpected broadening without the shoulder signals was observed below Tc at 1 T, and this broadening was quickly suppressed with increasing H. We construct the H–T phase diagram for H || b and H || c based on the NMR measurements and discuss possible SC states with the theoretical consideration. We suggest that the inhomogeneous SC state characterized by the broadening of the NMR spectrum originates from the spin degrees of freedom.
