arXiv subjects

H. Gotou

Publications and source records attributed to H. Gotou.

5 recordsLinked to original sources

arXiv2026

Three-dimensional zigzag correlations in the van der Waals Kitaev magnet RuBr$_3$

Ruthenium trihalides Ru$X_3$ ($X$ = Cl, Br, I) provide a tunable platform for Kitaev magnetism in two-dimensional van der Waals materials. Despite their similar crystal structures and zigzag antiferromagnetic order, RuBr$_3$ exhibits a higher N\'eel temperature ($T_N$) than RuCl$_3$, suggesting their distinct proximity to the Kitaev quantum spin liquid phase. Using Ru $L_3$-edge resonant x-ray scattering, we show that, while the long-range zigzag order in RuBr$_3$ disappears at $T_N$, the zigzag correlations that persist well above $T_N$ show a pronounced spectral weight redistribution along the interlayer direction. These results suggest that the enhanced interlayer magnetic interactions driven by the extended Br 4$p$ orbitals stabilize three-dimensional zigzag correlations in RuBr$_3$.

cond-mat.str-el↗

arXiv2024

$J=1/2$ Pseudospins and $d$-$p$ Hybridization in the Kitaev Spin Liquid Candidates Ru$X_3$ ($X$ = Cl, Br, I)

The recent synthesis of ruthenium trihalides Ru$X_3$ ($X$ = Cl, Br, I) has enlarged the set of material candidates for Kitaev spin liquid. The realization of Kitaev model necessitates the formation of $J=1/2$ pseudospins in the octahedral crystal field. We use Ru $L_3$-edge resonant inelastic x-ray scattering to investigate the evolution of multiplet structures in Ru$X_3$. We identified quasi-elastic magnetic correlations and spin-orbit transitions to the $J=3/2$ states without discernible trigonal splitting, thereby validating the $J=1/2$ description of magnetism in the Ru$X_3$ family. Lineshape broadening in RuI$_3$ provides evidence for its bulk metallicity in the vicinity of a bandwidth-controlled metal-insulator transition. Our results highlight the pivotal role of halogen $p$ orbitals in controlling the electronic properties of Ru$X_3$.

cond-mat.str-el↗

arXiv2017

Slater Insulator in Iridate Perovskites with Strong Spin-Orbit Coupling

The perovskite SrIrO3 is an exotic narrow-band metal owing to a confluence of the strengths of the spin-orbit coupling (SOC) and the electron-electron correlations. It has been proposed that topological and magnetic insulating phases can be achieved by tuning the SOC, Hubbard interactions, and/or lattice symmetry. Here, we report that the substitution of nonmagnetic, isovalent Sn4+ for Ir4+ in the SrIr1-xSnxO3 perovskites synthesized under high pressure leads to a metal-insulator transition to an antiferromagnetic (AF) phase at TN > 225 K. The continuous change of the cell volume as detected by x-ray diffraction and the lamda-shape transition of the specific heat on cooling through TN demonstrate that the metal-insulator transition is of second-order. Neutron powder diffraction results indicate that the Sn substitution enlarges an octahedral-site distortion that reduces the SOC relative to the spin-spin exchange interaction and results in the type-G AF spin ordering below TN. Measurement of high-temperature magnetic susceptibility shows the evolution of magnetic coupling in the paramagnetic phase typical of weak itinerant-electron magnetism in the Sn-substituted samples. A reduced structural symmetry in the magnetically ordered phase leads to an electron gap opening at the Brillouin zone boundary below TN in the same way as proposed by Slater.

cond-mat.str-el↗

arXiv2009

Spontaneous formation of a superconducting and antiferromagnetic hybrid state in SrFe2As2 under high pressure

We report a novel superconducting (SC) and antiferromagnetic (AF) hybrid state in SrFe2As2 revealed by 75As nuclear magnetic resonance (NMR) experiments on a single crystal under highly hydrostatic pressure up to 7 GPa. The NMR spectra at 5.4 GPa indicate simultaneous development of the SC and AF orders below 30 K. The nuclear spin-lattice relaxation rate in the SC domains shows a substantial residual density of states, suggesting proximity effects due to spontaneous formation of a nano-scale SC/AF hybrid structure. This entangled behavior is a remarkable example of a self-organized heterogeneous structure in a clean system.

cond-mat.supr-con↗

arXiv2008

CaCrO3: an anomalous antiferromagnetic metallic oxide

Combining infrared reflectivity, transport, susceptibility and several diffraction techniques, we find compelling evidence that CaCrO3 is a rare case of a metallic and antiferromagnetic transition-metal oxide with a three-dimensional electronic structure. LSDA calculations correctly describe the metallic behavior as well as the anisotropic magnetic ordering pattern of C type: The high Cr valence state induces via sizeable pd hybridization remarkably strong next-nearest neighbor interactions stabilizing this ordering. The subtle balance of magnetic interactions gives rise to magneto-elastic coupling, explaining pronounced structural anomalies observed at the magnetic ordering transition.

cond-mat.str-el↗