36 citations · 322 across the 29 of their papers we have counts for
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Novel Magnetoacoustic Resonance Technique for Exploring Hidden Quadrupoles in a Crystal Field Quartet
Mikito Koga, Masashige Matsumoto
Crystal field quartets with quadrupole degrees of freedom play a crucial role in hidden ordering systems, as exemplified by CeB. We present a novel magnetoacoustic resonance te…
Theory of Magnetoacoustic Resonance to Probe Multipole Effects Due to a Crystal Field Quartet
Mikito Koga, Masashige Matsumoto
We present a new method of acoustically driven resonance that probes octupole degrees of freedom as well as a quadrupole usually hidden by the magnetic properties of a crystal fiel…
Theory of Spin-Acoustic Resonance for Spin-3/2 Si Vacancy with Site Symmetry in Silicon Carbide
Mikito Koga, Masashige Matsumoto
Motivated by the recent acoustically driven spin resonance studies applied to silicon vacancy centers in silicon carbide, we theoretically investigate the spin--strain interaction…
Theory of Photon-Assisted Magnetoacoustic Resonance as a New Probe of Quadrupole Dynamics
Mikito Koga, Masashige Matsumoto
Motivated by the recent progress of phonon-mediated control in quantum spin devices, we propose a possibility of hybrid measurement using electron paramagnetic resonance (EPR) and…
Analysis of Magnetoacoustic Quadrupole Resonance and Application to Probe Quadrupole Degrees of Freedom in Quantum Magnets
Masashige Matsumoto, Mikito Koga
Motivated by the recent progress of high-frequency ultrasonic measurements, we propose a theory of magnetoacoustic resonance as a microscopic probe for quadrupole degrees of freedo…
Theoretical Study of Magnetoelectric Effects in Honeycomb Antiferromagnet Co4Nb2O9
Masashige Matsumoto, Mikito Koga
The honeycomb antiferromagnet Co4Nb2O9 is known to exhibit an interesting magnetoelectric effect that the electric polarization rotates at the twice speed in the opposite direction…
Symmetry Analysis of Magnetoelectric Effects in Honeycomb Antiferromagnet Co4Nb2O9
Masashige Matsumoto, Mikito Koga
Magnetoelectric effects in honeycomb antiferromagnet Co4Nb2O9 are investigated on the basis of symmetry analyses of Co ions in trigonal P-3c1 space group. For each Co ion, the poss…
Symmetry Analysis of Spin-Dependent Electric Dipole and Its Application to Magnetoelectric Effects
Masashige Matsumoto, Kosuke Chimata, Mikito Koga
Spin-dependent electric dipole operators are investigated group-theoretically for the emergence of an electric dipole induced by a single spin or by two spins, where the spin depen…
Effects of Impurities with Singlet-Triplet Configuration on Multiband Superconductors
Mikito Koga, Masashige Matsumoto, Hiroaki Kusunose
Roles of multipole degrees of freedom in multiband superconductors are investigated in a case of impurities whose low-lying states consist of singlet ground and triplet excited sta…
Effect of Impurities with Internal Structure on Multiband Superconductors - Possible Enhancement of Transition Temperature -
Mikito Koga, Masashige Matsumoto, Hiroaki Kusunose
We study inelastic (dynamical) impurity scattering effects in two-band superconductors with the same ( wave) or different ( wave) sign order parameters. We focus on…
Spin and orbital effects of Cooper pairs coupled to a single magnetic impurity
Mikito Koga, Masashige Matsumoto
The Kondo effect strongly depends on spin and orbital degrees of freedom of unconventional superconductivity. We focus on the Kondo effect in the -wave and $d_{x^2 - y…
Nonvanishing Local Moment in Triplet Superconductors
Mikito Koga, Masashige Matsumoto
The Kondo effect in a -wave superconductor is studied by applying the Wilson's numerical renormalization group method. In this type of superconductor with a full…
Hidden non-Fermi liquid behavior due to crystal field quartet
Mikito Koga
We study a realistic Kondo model for crystal field quartet ground states having magnetic and non-magnetic (quadrupolar) exchange couplings with conduction electrons, using the nume…
Crystal Field Triplets: A New Route to Non-Fermi Liquid Physics
Mikito Koga, Gergely Zarand, Daniel L. Cox
A model for crystal field triplet ground states on rare earth or actinide ions with dipolar and quadrupolar couplings to conduction electrons is studied for the first time with ren…
Small Energy Scale for Mixed-Valent Uranium Materials
Mikito Koga, Daniel L. Cox
We investigate a two-channel Anderson impurity model with a magnetic and a quadrupolar ground doublet, and a excited triplet. Using the numerical renormalizati…
Orbital Localization and Delocalization Effects in the U 5f^2 Configuration: Impurity Problem
Mikito Koga, Wenjian Liu, Michael Dolg +1
Anderson models, based on quantum chemical studies of the molecule of U(C_8H_8)_2, are applied to investigate the problem of an U impurity in a metal. The special point here is tha…