Weyl-Kondo semimetal behavior in the chiral structure phase of CeRhSn

Iwasa, Kazuaki*; Suyama, Kazuya*; Kawamura, Seiko; Nakajima, Kenji; Raymond, S.*; Steffens, P.*; Yamada, Akira*; Matsuda, Tatsuma*; Aoki, Yuji*; Kawasaki, Ikuto; et al.

Physical Review Materials (Internet), 7(1), p.014201_1 - 014201_11, 2023/01

https://doi.org/10.1103/PhysRevMaterials.7.014201

Successive phase transitions in IrSn (: La and Ce) investigated using neutron and X-ray diffraction

Nakazato, Seiya*; Iwasa, Kazuaki*; Hashimoto, Daisuke*; Shiozawa, Mami*; Kuwahara, Keitaro*; Nakao, Hironori*; Sagayama, Hajime*; Ishikado, Motoyuki*; Ohara, Takashi; Nakao, Akiko*; et al.

JPS Conference Proceedings (Internet), 30, p.011128_1 - 011128_6, 2020/03

https://doi.org/10.7566/JPSCP.30.011128

Magnetic-ordering propagation vectors of terbium hexaboride revisited

Iwasa, Kazuaki*; Iga, Fumitoshi*; Moyoshi, Taketo*; Nakao, Akiko*; Ohara, Takashi

Journal of the Physical Society of Japan, 87(6), p.064705_1 - 064705_5, 2018/06

https://doi.org/10.7566/JPSJ.87.064705

Second-order structural transition in the superconductor LaCoSn

Cheung, Y. W.*; Zhang, J. Z.*; Zhu, J. Y.*; Yu, W. C.*; Hu, Y. J.*; Wang, D. G.*; Otomo, Yuka*; Iwasa, Kazuaki*; Kaneko, Koji; Imai, Masaki*; et al.

Physical Review B, 93(24), p.241112_1 - 241112_5, 2016/06

AA2016-0058.pdf:0.95MB

https://doi.org/10.1103/PhysRevB.93.241112

Spin-orbit fluctuations in frustrated heavy-fermion metal LiVO

Tomiyasu, Keisuke*; Iwasa, Kazuaki*; Ueda, Hiroaki*; Niitaka, Seiji*; Takagi, Hidenori*; Kawamura, Seiko; Kikuchi, Tatsuya; Inamura, Yasuhiro; Nakajima, Kenji; Yamada, Kazuyoshi*

Physical Review Letters, 113(23), p.236402_1 - 236402_5, 2014/12

https://doi.org/10.1103/PhysRevLett.113.236402

Spin fluctuations were studied over a wide momentum () and energy () space in the frustrated -electron heavy-fermion metal LiVO by time-of-flight inelastic neutron scattering. We observed the overall evolutions near the characteristic = 0.6 peak and found another weak broad magnetic peak around 2.4 . The data are described by a simple response function, a partially delocalized magnetic form factor, and antiferromagnetic short-range spatial correlations, indicating that heavy-fermion formation is attributable to spin-orbit fluctuations with orbital hybridization.

Magnetic phase diagrams of YVO and TbVO under high pressure

Bizen, Daisuke*; Nakao, Hironori*; Iwasa, Kazuaki*; Murakami, Yoichi*; Osakabe, Toyotaka; Fujioka, Jun*; Yasue, Toshio*; Miyasaka, Shigeki*; Tokura, Yoshinori*

Journal of the Physical Society of Japan, 81(2), p.024715_1 - 024715_6, 2012/02

https://doi.org/10.1143/JPSJ.81.024715

The magnetic phase diagrams for VO ( = Y, Tb) were determined by low temperature and high pressure neutron-diffraction techniques. We found that the magnetic ground state in TbVO changes from -type spin ordering (-SO) to -type spin ordering (-SO) on application of pressure. The transition of the magnetic ground state also indicates that the ground state of the orbital ordering changes from -type orbital ordering (-OO) to -type orbital ordering (-OO). In YVO, the -SO and -OO phases set in simultaneously up to 6.2 GPa, and the disorder-[-SO, -OO] phase transition appears above 6 GPa. This is the first observation of a simultaneous spin and orbital order-disorder phase transition in perovskite-type transition-metal oxides MO. The [-SO, -OO] phase is strongly stabilized with increasing pressure, and both the covalency effect and the superexchange interaction play roles in this stabilization.

The Unconventional superconductivity of skutterudite PrOsSb; Time-reversal symmetry breaking and adjacent field-induced quadrupole ordering

Aoki, Yuji*; Tayama, Takashi*; Sakakibara, Toshiro*; Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kogi, Masafumi*; Higemoto, Wataru; MacLaughlin, D. E.*; Sugawara, Hitoshi*; Sato, Hideyuki*

Journal of the Physical Society of Japan, 76(5), p.051006_1 - 051006_13, 2007/05

https://doi.org/10.1143/JPSJ.76.051006

This review presents a summary and evaluation of the experimental properties of unconventional superconductivity in PrOsSb. After a brief introduction of filled skutterudites, we argue that the normal-state properties of PrOsSb are quite different from ordinary heavy-fermion superconductors.

Resonant X-ray scattering of PrRuP

Ishii, Kenji; Tsutsui, Satoshi*; Hao, L.*; Hasegawa, Tomoo*; Iwasa, Kazuaki*; Tsubota, Masami; Inami, Toshiya; Murakami, Yoichi*; Saha, S. R.*; Sugawara, Hitoshi*; et al.

Journal of Magnetism and Magnetic Materials, 310(2, Part1), p.e178 - e180, 2007/03

PrRuP shows a metal-insulator (MI) transition at 62 K accompanied by a structural phase transition. Because LaRuP without electrons does not shows the MI transition, electrons in the Pr atom plays an important role in the transition. In order to elucidate a modulation of electronic states of Pr, we have carried out a resonant X-ray scattering study of PrRuP at Pr - and -edges. Below , resonant signal at the absorption main-edge was successfully observed at the superlattice reflections of the modulation vector in addition to the energy-independent component from the lattice distortion. Because the reflection contains the difference of anomalous scattering factors between two Pr atoms in the unit cell, two different electronic states are actually ordered below . Furthermore we found that the polarization of X-ray is mostly unrotated even at the resonance, which indicates that the resonant scattering in PrRuP is almost isotropic.

Inelastic neutron scattering study on low-energy excitations of the heavy-fermion superconductor PrOsSb

Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kogi, Masafumi*; Kaneko, Koji; Metoki, Naoto; Raymond, S.*; Masson, M.-A.*; Flouquet, J.*; Sugawara, Hitoshi*; Aoki, Yuji*; et al.

Physica B; Condensed Matter, 385-386(Part 1), p.82 - 84, 2006/11

https://doi.org/10.1016/j.physb.2006.05.109

We report inelastic neutron scattering experiments performed to investigate the low energy magnetic excitations on single crystals of the heavy-fermion superconductor PrOsSb. The observed excitation clearly softens at a wave vector Q=(1,0,0), which is the same as the modulation vector of the field-induced antiferro-quadrupolar ordering, and its intensity at Q=(1,0,0) is smaller than that around the zone center. This result directly evidences that this excitonic behavior is derived mainly from nonmagnetic quadrupolar interactions. Furthermore, the narrowing of the linewidths of the excitations below the superconducting transition temperature indicates the close connection between the superconductivity and the excitons.

Magnetic excitations in the heavy-fermion superconductor PrOsSb

Raymond, S.*; Flouquet, J.*; Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kogi, Masafumi*; Kaneko, Koji; Metoki, Naoto; Sugawara, Hitoshi*; Aoki, Yuji*; Sato, Hideyuki*

Physica B; Condensed Matter, 359-361, p.898 - 900, 2005/06

https://doi.org/10.1016/j.physb.2005.01.256

The low lying magnetic excitations of the unconventional heavy fermion superconductor PrOsSb were studied by inelastic neutron scattering on single crystalline sample. The crystal field excitation first evidenced at 0.7 meV on powder samples is found to have a minimum of energy at the zone boundary corresponding to the wavevector of antiferro-quadrupolar instability. The evolution of the magnetic excitation spectrum under magnetic field confirms the singlet ground state.