Room-temperature flexible manipulation of the quantum-metric structure in a topological chiral antiferromagnet

Han, J.*; Uchimura, Tomohiro*; Araki, Yasufumi; Yoon, J.-Y.*; Takeuchi, Yutaro*; Yamane, Yuta*; Kanai, Shun*; Ieda, Junichi; Ohno, Hideo*; Fukami, Shunsuke*

Nature Physics, 20(7), p.1110 - 1117, 2024/07

https://doi.org/10.1038/s41567-024-02476-2

Quantum metric and Berry curvature are two fundamental and distinct factors to describe the geometry of quantum eigenstates. While Berry curvature is known for playing crucial roles in several condensed-matter states, quantum metric, which was predicted to induce new classes of topological phenomena, has rarely been touched, particularly in an ambient circumstance. Using a topological chiral antiferromagnet MnSn adjacent to Pt, at room temperature, we successfully manipulate the quantum-metric structure of electronic states through its interplay with the nanoscale spin texture at the MnSn/Pt interface. This is manifested by a time-reversal-odd second-order Hall effect that is robust against extrinsic electron scattering, in contrast to any transport effects from the Berry curvature. We also verify the flexibility of controlling the quantum-metric structure, as the interacting spin texture can be tuned by moderate magnetic fields or by interface engineering via spin-orbit interactions. Our work paves a way for harnessing the quantum-metric structure to unveil emerging topological physics in practical environments and to build applicable nonlinear devices.

Discrete degeneracies distinguished by the anomalous Hall effect in a metallic kagome ice compound

Zhao, K.*; Tokiwa, Yoshifumi; Chen, H.*; Gegenwart, P.*

Nature Physics, 20(3), p.442 - 449, 2024/03

https://doi.org/10.1038/s41567-023-02307-w

In magnetic crystals, despite the explicit breaking of time-reversal symmetry, two equilibrium states related by time reversal are always energetically degenerate. In ferromagnets, this time-reversal degeneracy is reflected in the hysteresis of the magnetic field dependence of the magnetization and, if metallic, in that of the anomalous Hall effect (AHE). Under time-reversal, both these quantities change signs but not their magnitude. Here we show that a time-reversal-like degeneracy appears in the metallic kagome spin ice HoAgGe when magnetic fields are applied parallel to the kagome plane. We find vanishing hysteresis in the field dependence of the magnetization at low temperature, but finite hysteresis in the field-dependent AHE. This suggests the emergence of states with nearly the same energy and net magnetization but different sizes of the AHE and of the longitudinal magnetoresistance. By analysing the experimental data and a minimal tight-binding model, we identify a time-reversal-like operation connecting these near-degenerate states, which is related to the non-trivial distortion of the kagome lattice in HoAgGe. Our work demonstrates the diagnostic power of transport phenomena for identifying hidden symmetries in frustrated spin systems.

Chiral symmetry restoration at high matter density observed in pionic atoms

Nishi, Takahiro*; Hashimoto, Tadashi; 46 of others*

Nature Physics, 19(6), p.788 - 793, 2023/06

https://doi.org/10.1038/s41567-023-02001-x

Characterization of the shape-staggering effect in mercury nuclei

Marsh, B. A.*; Day Goodacre, T.*; Tsunoda, Yusuke*; Andreyev, A. N.; 41 of others*

Nature Physics, 14(12), p.1163 - 1167, 2018/12

https://doi.org/10.1038/s41567-018-0292-8

Thermodynamic evidence for nematic superconductivity in CuBiSe

Yonezawa, Shingo*; Tajiri, Kengo*; Nakata, Suguru*; Nagai, Yuki; Wang, Z.*; Segawa, Koji*; Ando, Yoichi*; Maeno, Yoshiteru*

Nature Physics, 13(2), p.123 - 126, 2017/02

https://doi.org/10.1038/nphys3907

no abstracts in English

Spin hydrodynamic generation

Takahashi, Ryo*; Matsuo, Mamoru; Ono, Masao; Harii, Kazuya; Chudo, Hiroyuki; Okayasu, Satoru; Ieda, Junichi; Takahashi, Saburo*; Maekawa, Sadamichi; Saito, Eiji

Nature Physics, 12, p.52 - 56, 2016/01

https://doi.org/10.1038/nphys3526

Degenerate Fermi and non-Fermi liquids near a quantum critical phase transition

Kambe, Shinsaku; Sakai, Hironori; Tokunaga, Yo; Lapertot, G.*; Matsuda, Tatsuma*; Knebel, G.*; Flouquet, J.*; Walstedt, R. E.*

Nature Physics, 10(11), p.840 - 844, 2014/11

https://doi.org/10.1038/nphys3101

In new observations reported here, we find that coexisting, static Fermi liquid and non-Fermi liquid states are a key feature of the QCPT in YbRhSi. By means of nuclear magnetic resonance (NMR) spin-lattice relaxation time measurements on a single crystal sample, it is revealed that the FL and NFL states are invariant,while their relative proportion in a crossover is field dependent near the QCPT. Such a pair of states has remained hidden in Ce compounds, owing presumably to short lifetimes for the two states. A new scaling law for the occupation ratio of the two states is derived, and could be widely applicable to Kondo-lattice systems

Polaron spin current transport in organic semiconductors

Watanabe, Shun*; Ando, Kazuya*; Kang, K.*; Mooser, S.*; Vaynzof, Y.*; Kurebayashi, Hidekazu*; Saito, Eiji; Sirringhaus, H.*

Nature Physics, 10(4), p.308 - 313, 2014/04

https://doi.org/10.1038/nphys2901

Charge-induced vortex lattice instability

Mounce, A. M.*; Oh, S.*; Mukhopadhyay, S.*; Halperin, W. P.*; Reyes, A. P.*; Kuhns, P. L.*; Fujita, Kazuhiro*; Ishikado, Motoyuki; Uchida, Shinichi*

Nature Physics, 7(2), p.125 - 128, 2011/02

https://doi.org/10.1038/nphys1835

It has been predicted that superconducting vortices should be electrically charged and that this effect is particularly enhanced for high-temperature superconductors. Hall effect and nuclear magnetic resonance (NMR) experiments suggest the existence of charge accumulation in the vortex core, but the effects are small and the interpretation controversial. Here we show that the Abrikosov vortex lattice, characteristic of the mixed state of superconductors, will become unstable at a sufficiently high magnetic field if there is charge trapped on the vortex core. Our NMR measurements of the magnetic fields generated by vortices in BiSrCaCuO single crystals provide evidence for an electrostatically driven vortex lattice reconstruction with the magnitude of charge on each vortex pancake of , depending on doping, in line with theoretical estimates.

Itinerant to localized transition of electrons in the antiferromagnetic superconductor UPdAl

Fujimori, Shinichi; Saito, Yuji; Okane, Tetsuo; Fujimori, Atsushi*; Yamagami, Hiroshi*; Haga, Yoshinori; Yamamoto, Etsuji; Onuki, Yoshichika*

Nature Physics, 3(9), p.618 - 622, 2007/09

https://doi.org/10.1038/nphys651

In heavy Fermion (HF) compounds, electrons show both itinerant and localized behaviour depending on temperature. Above the characteristic temperature , their magnetic properties are well described by the completely "localized" -electron models. On the other hand, well below , their Fermi surfaces (FS's) have been explained well by the "itinerant" -electron model. These two models assume totally different natures of -electrons, and how they transform between these states as a function of temperatures has never been understood on the level of their electronic structures. Here we have studied the band structure of the HF antiferromagnetic superconductor UPdAl well below and above by angle-resolved photoelectron spectroscopy (ARPES), and have found that the -bands, which form the FS's at low temperatures, are excluded from FS's at high temperatures.