北海道大学 · 物理学・天文学
Megumi Yatsushiro教授の研究室では、電子系の多様な自由度（スピン、電荷、軌道、磁気モーメントなど）の相関が生じる非代替的電子秩序状態に注目し、多極モーメントの統一的記述に基づいた物性の理解を進めています。特に、磁気モーメントのトロイダル成分や奇性パリティを持つ多極秩序が示す新奇な磁気・電気的性質や、非線形輸送・NMR/NQRのスペクトルに及ぼす影響を理論的に解明しています。空間反転と時間反転の両対称性が破れた系における新規物性の解明が、主な研究テーマです。
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Mutual interplay between the electronic degrees of freedom in solids, such as charge, spin, orbital, sublattice, and bond degrees of freedom, is a source of cross-correlated phenomena with unconventional electronic ordered states. Such degrees of freedom can be described by four types of multipoles (electric, magnetic, magnetic toroidal, and electric toroidal) in a unified way, which enable us to tightly connect the microscopic degrees of freedom with macroscopic physical responses in a transpar
A magnetic toroidal moment is a fundamental electronic degree of freedom in the absence of both spatial inversion and time-reversal symmetries and gives rise to novel multiferroic and transport properties. We elucidate essential model parameters of the nonlinear transport in the space-time $(\mathcal{PT})$ symmetric collinear antiferromagnetic metals accompanying a magnetic toroidal moment. By analyzing the longitudinal and transverse components of the second-order nonlinear conductivity on a tw
We study theoretically NQR and NMR spectra in the presence of odd-parity multipoles originating from staggered antiferromagnetic and antiferroquadrupole orderings. For the $f$-electron metal CeCoSi, which is a candidate hosting odd-parity multipoles, we derive an effective hyperfine field acting on a Co nucleus generated from electronic origin multipole moments of the Ce ion in zero and nonzero magnetic fields. We elucidate that emergent odd-parity multipoles give rise to sublattice-dependent sp
We investigate the stability of the multipolar orderings in $f$-electron material CeCoSi based on a self-consistent mean-field calculation for the effective localized model. This material has two ordered phases in the temperature-pressure phase diagram: the antiferromagnetic phase and the nonmagnetic phase, the latter of which has been suggested to be an antiferroquadrupolar phase. Meanwhile, the origin of the antiferroquadrupolar phase has been unclear, since a quadrupole degree of freedom is p
Mutual interplay between the electronic degrees of freedom in solids, such as charge, spin, orbital, sublattice, and bond degrees of freedom, is a source of cross-correlated phenomena with unconventional electronic ordered states. Such degrees of freedom can be described by four types of multipoles (electric, magnetic, magnetic toroidal, and electric toroidal) in a unified way, which enable us to tightly connect the microscopic degrees of freedom with macroscopic physical responses in a transpar
A magnetic toroidal moment is a fundamental electronic degree of freedom in the absence of both spatial inversion and time-reversal symmetries and gives rise to novel multiferroic and transport properties. We elucidate essential model parameters of the nonlinear transport in the space-time ($\mathcal{PT}$) symmetric collinear antiferromagnetic metals accompanying a magnetic toroidal moment. By analyzing the longitudinal and transverse components of the second-order nonlinear conductivity on a tw
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