Hokkaido University · Physics and Astronomy
Professor Megumi Yatsushiro's research lab specializes in strongly correlated electron systems, with a focus on unconventional electronic orderings driven by the interplay of multiple electronic degrees of freedom—such as spin, charge, orbital, and multipole orders. The lab employs group-theoretical classification and theoretical many-body methods to uncover the microscopic origins of exotic quantum phases, particularly in f-electron materials like CeCoSi. A central theme is the role of multipoles—especially magnetic toroidal and odd-parity multipoles—in generating novel multiferroic and nonlinear transport phenomena, often in systems lacking inversion or time-reversal symmetry. The lab also investigates emergent phenomena through NMR/NQR spectroscopy and nonlinear response theory, aiming to bridge microscopic electronic structure with macroscopic observables.
Figures are computed from collected data and may differ slightly.
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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