Yuichi Ohnuma
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View article: Violation of the magnonic Wiedemann-Franz law in the strong nonlinear regime
Violation of the magnonic Wiedemann-Franz law in the strong nonlinear regime Open
The celebrated Wiedemann-Franz (WF) law which governs the relation between\ncharge and heat transport traces back to the experimental discovery in 1853 by\nWiedemann and Franz. Despite the fundamental difference of the\nquantum-statistical…
View article: Direct and alternating magnon spin currents across a junction interface irradiated by linearly polarized laser
Direct and alternating magnon spin currents across a junction interface irradiated by linearly polarized laser Open
The developments in the field of quantum optics raise expectations that\nlaser-matter coupling is a promising building block for magnonics. Here, we\npropose a method for the generation of direct and alternating spin currents of\nmagnons a…
View article: Optical polarimetric measurement of surface acoustic waves
Optical polarimetric measurement of surface acoustic waves Open
A surface acoustic wave (SAW) is utilized in diverse fields ranging from physics, engineering, to biology for transducing, sensing, and processing various signals. Optical measurement of the SAW provides valuable information since the ampl…
View article: Erratum: Spin Current Noise of the Spin Seebeck Effect and Spin Pumping [Phys. Rev. Lett. <b>120</b>, 037201 (2018)]
Erratum: Spin Current Noise of the Spin Seebeck Effect and Spin Pumping [Phys. Rev. Lett. <b>120</b>, 037201 (2018)] Open
This corrects the article DOI: 10.1103/PhysRevLett.120.037201.
View article: Magnonic thermal transport using the quantum Boltzmann equation
Magnonic thermal transport using the quantum Boltzmann equation Open
We present a formula for thermal transport in the bulk of Bose systems based\non the quantum Boltzmann equation (QBE). First, starting from the quantum\nkinetic equation and using the Born approximation for impurity scattering, we\nderive …
View article: Optical polarimetric imaging of surface acoustic waves
Optical polarimetric imaging of surface acoustic waves Open
Surface acoustic wave (SAW) is utilized in diverse fields ranging from physics, engineering, to biology, for transducing, sensing and processing various signals. Optical imaging of SAW provides valuable information since the amplitude and …
View article: Microscopic theory of spin Hall magnetoresistance
Microscopic theory of spin Hall magnetoresistance Open
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 insulator in terms of spin susceptibilities. We reveal that SMR is …
View article: Author Correction: Record thermopower found in an IrMn-based spintronic stack
Author Correction: Record thermopower found in an IrMn-based spintronic stack Open
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
View article: Spin hydrodynamic generation in graphene
Spin hydrodynamic generation in graphene Open
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 motion of the electron fluid resembles the flow of classical …
View article: Microscopic theory of spin transport at the interface between a superconductor and a ferromagnetic insulator
Microscopic theory of spin transport at the interface between a superconductor and a ferromagnetic insulator Open
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 formulas for the spin current and spin-current noise induc…
View article: $1/3$-Suppression of Magnonic Shot Noise in Diffusive Insulating Magnets
$1/3$-Suppression of Magnonic Shot Noise in Diffusive Insulating Magnets Open
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 of bosons and fermions. To this end, starting from a quantu…
View article: Asymmetric quantum shot noise in magnon transport
Asymmetric quantum shot noise in magnon transport Open
We study a frequency-dependent noise-to-current ratio for asymmetric,\nsymmetric, and noncommutative current-noise in a ferromagnetic insulating\njunction, and extract quantum-mechanical properties of magnon transport at low\ntemperatures.…
View article: Magnonic noise and Wiedemann-Franz law
Magnonic noise and Wiedemann-Franz law Open
We theoretically establish mutual relations among magnetic momentum, heat,\nand fluctuations of propagating magnons in a ferromagnetic insulating junction\nin terms of noise and the bosonic Wiedemann-Franz (WF) law. Using the\nSchwinger-Ke…
View article: Nuclear spin pumping by pulling effect
Nuclear spin pumping by pulling effect Open
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 nonequilibrium Green's function method. The spin current gene…
View article: Dirac-Surface-State Modulated Spin Dynamics in a Ferrimagnetic Insulator at Room Temperature
Dirac-Surface-State Modulated Spin Dynamics in a Ferrimagnetic Insulator at Room Temperature Open
This work demonstrates markedly modified spin dynamics of magnetic insulator (MI) by the spin momentum-locked Dirac surface states of the adjacent topological insulator (TI), which can be harnessed for spintronic applications. As the Bi co…
View article: Dirac surface state–modulated spin dynamics in a ferrimagnetic insulator at room temperature
Dirac surface state–modulated spin dynamics in a ferrimagnetic insulator at room temperature Open
Spin dynamics of magnetic insulator is markedly modulated by the Dirac surface states in the adjacent topological insulator.
View article: Spin Current Noise of the Spin Seebeck Effect and Spin Pumping
Spin Current Noise of the Spin Seebeck Effect and Spin Pumping Open
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. Starting with a simple ferromagnet-insulator-(FI-)NM interface m…
View article: Theory of the spin Peltier effect
Theory of the spin Peltier effect Open
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 function method is presented. Spin current and heat current …
View article: Theory of spin hydrodynamic generation
Theory of spin hydrodynamic generation Open
Spin-current generation by fluid motion is theoretically investigated. Based\non quantum kinetic theory, the spin-diffusion equation coupled with fluid\nvorticity is derived. We show that spin currents are generated by the vorticity\ngradi…
View article: Spin transport in half-metallic ferromagnets
Spin transport in half-metallic ferromagnets Open
We theoretically investigate spin transport in half-metallic ferromagnets at\nfinite temperatures. The side-jump and skew-scattering contributions to spin\nHall conductivity are derived using the Kubo formula. The electron-magnon\ninteract…
View article: Magnon instability driven by heat current in magnetic bilayers
Magnon instability driven by heat current in magnetic bilayers Open
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 temperature bias. Employing many-body theory for investigating th…