133 citations · 693 across the 21 of their papers we have counts for
21 papers
Violation of the magnonic Wiedemann-Franz law in the strong nonlinear regime
Kouki Nakata, Yuichi Ohnuma, Se Kwon Kim
The celebrated Wiedemann-Franz (WF) law which governs the relation between charge and heat transport traces back to the experimental discovery in 1853 by Wiedemann and Franz. Despi…
Direct and alternating magnon spin currents across a junction interface irradiated by linearly polarized laser
Kouki Nakata, Yuichi Ohnuma
The developments in the field of quantum optics raise expectations that laser-matter coupling is a promising building block for magnonics. Here, we propose a method for the generat…
Magnonic thermal transport using the quantum Boltzmann equation
Kouki Nakata, Yuichi Ohnuma
We present a formula for thermal transport in the bulk of Bose systems based on the quantum Boltzmann equation (QBE). First, starting from the quantum kinetic equation and using th…
Optical polarimetric measurement of surface acoustic waves
Kotaro Taga, Ryusuke Hisatomi, Yuichi Ohnuma +4
Surface acoustic wave (SAW) is utilized in diverse fields ranging from physics, engineering, to biology, for transducing, sensing and processing various signals. Optical measuremen…
Spin hydrodynamic generation in graphene
Mamoru Matsuo, Denis A. Bandurin, Yuichi Ohnuma +2
Graphene hosts an ultra-clean electronic system with electron-electron collisions being the dominant source of scattering above liquid nitrogen temperatures. In this regime, the mo…
Microscopic Theory of the Spin Hall Magnetoresistance
Takeo Kato, Yuichi Ohnuma, Mamoru Matsuo
We consider a microscopic theory for the spin Hall magnetoresistance (SMR). We generally formulate a spin conductance at an interface between a normal metal and a magnetic insulato…
Angular momentum compensation manipulation to room temperature of the ferrimagnet HoDyFeO detected by the Barnett effect
Masaki Imai, Hiroyuki Chudo, Masao Ono +5
We demonstrate that the angular momentum compensation temperature , at which the net angular momentum in the sample disappears, can be controlled in HoFeO by pa…
Universal -suppression of magnonic shot noise in diffusive insulating magnets
Kouki Nakata, Yuichi Ohnuma, Mamoru Matsuo
Extending a Boltzmann-Langevin theory to magnons, we show a universality of current-noise suppression in diffusive systems against the difference of quantum-statistical properties…
Asymmetric quantum shot noise in magnon transport
Kouki Nakata, Yuichi Ohnuma, Mamoru Matsuo
We study a frequency-dependent noise-to-current ratio for asymmetric, symmetric, and noncommutative current-noise in a ferromagnetic insulating junction, and extract quantum-mechan…
Microscopic theory of spin transport at the interface between the superconductor and a ferromagnetic insulator
T. Kato, Y. Ohnuma, M. Matsuo +3
We theoretically investigate spin transport at the interface between the ferromagnetic insulator(FI) and a superconductor(SC). Considering a simple FI-SC interface model, we derive…
Nuclear spin pumping by pulling effect
Y. Ohnuma, S. Maekawa, M. Matsuo
The nuclear-to-electron spin angular momentum conversion via hyperfine coupling in a normal metal (NM)/ferromagnet (FM) bilayer system is theoretically investigated by using the no…
Magnonic Noise and Wiedemann-Franz Law
Kouki Nakata, Yuichi Ohnuma, Mamoru Matsuo
We theoretically establish mutual relations among magnetic momentum, heat, and fluctuations of propagating magnons in a ferromagnetic insulating junction in terms of noise and the…
Dirac-Surface-State Modulated Spin Dynamics in a Ferrimagnetic Insulator at Room Temperature
Chi Tang, Qi Song, Cui-Zu Chang +10
This work demonstrates dramatically modified spin dynamics of magnetic insulator (MI) by the spin-momentum locked Dirac surface states of the adjacent topological insulator (TI) wh…
Observation of gyromagnetic reversal
Masaki Imai, Yudai Ogata, Hiroyuki Chudo +6
We report direct observation of gyromagnetic reversal, which is the sign change of gyromagnetic ratio in a ferrimagnet HoFeO, by using the Barnett effect measurement…
Spin current noise of the spin Seebeck effect and spin pumping
M. Matsuo, Y. Ohnuma, T. Kato +1
We theoretically investigate the fluctuation of a pure spin current induced by the spin Seebeck effect and spin pumping in a normal metal (NM)/ferromagnet (FM) bilayer system. Star…
Theory of spin Peltier effect
Y. Ohnuma, M. Matsuo, S. Maekawa
A microscopic theory of the spin Peltier effect in a bilayer structure comprising a paramagnetic metal (PM) and a ferromagnetic insulator (FI) based on the nonequilibrium Green's f…
Theory of spin hydrodynamic generation
Mamoru Matsuo, Yuichi Ohnuma, Sadamichi Maekawa
Spin-current generation by fluid motion is theoretically investigated. Based on quantum kinetic theory, the spin-diffusion equation coupled with fluid vorticity is derived. We show…
Spin transport in half-metallic ferromagnets
Y. Ohnuma, M. Matsuo, S. Maekawa
We theoretically investigate spin transport in half-metallic ferromagnets at finite temperatures. The side-jump and skew-scattering contributions to spin Hall conductivity are deri…
Magnon instability driven by heat current in magnetic bilayers
Yuichi Ohnuma, Hiroto Adachi, Eiji Saitoh +1
We theoretically demonstrate that, in a ferromagnet/paramagnet bilayer, a magnon instability accompanied by a gigahertz microwave emission can be driven simply by means of a temper…
Enhanced DC Spin Pumping into a Fluctuating Ferromagnet near Tc
Yuichi Ohnuma, Hiroto Adachi, Eiji Saitoh +1
A linear-response formulation of the dc spin pumping, i.e., a spin injection from a precessing ferromagnet into an adjacent spin sink, is developed in view of describing many-body…
Spin Seebeck effect in antiferromagnets and compensated ferrimagnets
Yuichi Ohnuma, Hiroto Adachi, Eiji Saitoh +1
We theoretically investigate the spin Seebeck effect (SSE) in antiferromagnets and ferrimagnets, and show that the SSE vanishes in antiferromagnets but survives in ferrimagnets eve…