arXiv subjects

Mamoru Matsuo

Publications and source records attributed to Mamoru Matsuo.

At least 37 records · Page 2Linked to original sources

arXiv2025

Fluctuations in Spin Dynamics Excited by Pulsed Light

We theoretically investigate nonequilibrium spin fluctuations in a ferromagnet induced by a light pulse. Using a Lindblad equation consistent with the Landau-Lifshitz-Gilbert equation, we compute the autocorrelation function of magnetization. Our analysis reveals that this function comprises both thermal and nonequilibrium components. To examine the latter in detail, we introduce a Fano factor similar to nonequilibrium current noise in electronic circuits. We demonstrate that this factor encapsulates insights into the transfer of spin units to the environment. Our findings lay the groundwork for nonequilibrium spin noise spectroscopy, offering valuable insights into spin relaxation dynamics.

cond-mat.mes-hall↗

arXiv2025

Spin pumping effect in non-Fermi liquid metals

Spin pumping effect is a sensitive and well-established experimental method in two-dimensional (2D) magnetic materials. We propose that spin pumping effect can be a valuable probe for non-Fermi liquid (NFL) behaviors at the 2D interface of magnetic heterostructures. We show that the modulations of ferromagnetic resonance exhibit power-law scalings in frequency and temperature for NFL metals induced near a quantum critical point (QCP). At the Ising nematic QCP, we demonstrate that the enhanced Gilbert damping coefficient $δα$ acquires negative power-law exponents in distinct frequency regimes. The exponents convey universal parameters inherited from the QCP and reflect the non-quasiparticle nature of the spin carriers in the NFL metal. At finite temperature, we show that the Gilbert damping mechanism is restored in the quantum critical regime and $δα$ measures the temperature dependence of the correlation length. Our theoretical proposal has the potential to stimulate the development of an interdisciplinary research domain where insights from non-equilibrium spin physics in spintronics are integrated into strongly correlated matter.

cond-mat.str-el↗

arXiv2025

Gyromagnetic Angular Momentum Interconversion in Neutron Stars

We propose a novel mechanism for angular momentum (AM) exchange between the crust and core of a neutron star (NS) via the gyromagnetic effect. Using extended hydrodynamics, we model the star by incorporating macroscopic AM and microscopic AM originating from neutron orbital and spin AM. We reveal that macroscopic dynamics in the crust can inform microscopic AM in the core leading to neutron spin polarization, and offer alternative scenario of (anti-)glitches. This work highlights the overlooked multi-scale AM interconversions in NS physics, paving the way for gyromagnetic astrophysics.

astro-ph.HE↗

arXiv2025

Directional propagation of quantum Hall viscous fluid by nano-structural engineering

We present a microscopic theory of the viscous electron fluid in the quantum Hall state based on the nonequilibrium Green's function method and the von Neumann lattice representation. This approach permits the formulation of hydrodynamic equations in the strong field regime that accommodates arbitrary boundary conditions. We demonstrate nonreciprocal transport resulting from the interplay between magnetic field-induced viscosity and device geometry in a notched system. Our results will offer a powerful tool for studying the nonperturbative effects of magnetic fields on electron viscous fluids.

cond-mat.mes-hall↗

arXiv2025

Spin current generation due to differential rotation

We study nonequilibrium spin dynamics in differentially rotating systems, deriving an effective Hamiltonian for conduction electrons in the comoving frame. In contrast to conventional spin current generation mechanisms that require vorticity, our theory describes spins and spin currents arising from differentially rotating systems regardless of vorticity. We demonstrate the generation of spin currents in differentially rotating systems, such as liquid metals with Taylor-Couette flow. Our alternative mechanism will be important in the development of nanomechanical spin devices.

cond-mat.mes-hall↗

arXiv2025

Thermomagnetic anomalies in quantum magnon transport caused by tunable junction geometries in cold atomic systems

We study magnon-driven spin and heat transport in a magnetic linear junction (MLJ) formed by two ferromagnets in optical lattices linked via linearly aligned bonds. Using the Schwinger-Keldysh formalism, we uncover that under weak effective Zeeman fields, where Bose-Einstein statistics of magnons dominate, magnonic criticality dramatically enhances spin and thermal conductances. These singular transport properties depend on the junction geometry, and the transport properties qualitatively differ between the linear junction in this study and the point contact in our previous work. The quantum-enhanced conductances result in the breakdown of the magnonic Wiedemann-Franz (WF) law. In the classical regime at temperatures much lower than magnon energy gaps, we find that a magnonic Lorenz number becomes independent of temperature yet dependent on junction geometry, sharply contrasting with the universal WF law for Fermi liquids. We also find that the interface geometry of MLJ decouples spin and heat relaxations between ferromagnets with decay times insensitive to temperature and effective Zeeman fields. These dynamics reveal junction-geometry-sensitive magnon transport distinct from Fermi liquids, paving the way for new avenues in thermomagnetic research leveraging the tunability of cold atomic systems.

cond-mat.quant-gas↗

arXiv2024

Spin Seebeck Effect in Graphene

We develop a microscopic theory of the spin Seebeck effect (SSE) at the interface of a bilayer system of a ferromagnetic insulator and graphene. We compare the tunneling spin current at the interface because of the SSE and the spin pumping (SP), where the SSE and SP are induced by the temperature gradient and the microwave irradiation, respectively. We demonstrate that the thermally driven SSE exhibits a quantum oscillation pattern similar to that predicted in coherently driven SP. Additionally, we show a peak shift of the quantum oscillation owing to the contribution of thermally excited magnons with higher frequencies, which becomes particularly pronounced at higher temperatures.

cond-mat.mes-hall↗

arXiv2024

Theory of spin pumping and inverse Rashba-Edelstein effect in a two-dimensional electron gas

We theoretically investigate spin transport in a junction system composed of a ferromagnetic insulator (FI) and a two-dimensional electron gas (2DEG) with both Rashba and Dresselhaus spin-orbit interactions. We briefly present our findings on spin pumping into the 2DEG under microwave irradiation and subsequent current generation via the inverse Rashba-Edelstein effect. We highlight the crucial role of vertex corrections in the theoretical description of these effects.

cond-mat.mes-hall↗

arXiv2024

Chirality-induced Phonon-Spin Conversion at an Interface

We consider spin injection driven by nonequilibrium chiral phonons from a chiral insulator into an adjacent metal. Phonon-spin conversion arises from the coupling of the electron spin with the microrotation associated with chiral phonons. We derive a microscopic formula for the spin injection rate at a metal-insulator interface. Our results clearly illustrate the microscopic origin of spin current generation by chiral phonons and may lead to a breakthrough in the development of spintronic devices without heavy elements.

cond-mat.mes-hall↗

arXiv2024

Spin pumping into quantum spin chains

We theoretically investigate spin pumping into a quantum easy-plane ferromagnetic spin chain system. This quantum spin chain is effectively described by the Tomonaga-Luttinger (TL) liquid despite the ferromagnetic exchange interaction because of the easy-plane magnetic anisotropy. This TL liquid state has an extremely strong interaction that is hardly realized in other quantum antiferromagnetic chain systems or weakly interacting electron systems. We show how the strongly interacting TL liquid affects the ferromagnetic resonance that occurs in the ferromagnetic insulator. In particular, we discuss the dependence of the Gilbert damping on the temperature and the junction length. The Gilbert damping allows us to extract information about the above-mentioned strong interaction within the quantum ferromagnetic spin chain. We also point out that a well-known compound CsCuCl$_3$ will be suitable for the realization of our setup.

cond-mat.str-el↗

arXiv2024

Theory of the inverse Rashba-Edelstein effect induced by thermal spin injection

We theoretically consider a junction composed of a ferromagnetic insulator (FI) and a two-dimensional electron gas (2DEG) with Rashba- and Dresselhaus-type spin-orbit interactions. Using the Boltzmann equation, we calculate an electric current in 2DEG induced by the inverse Rashba-Edelstein effect when imposing the temperature difference between FI and 2DEG. We clarify how the induced current depends on the magnetization direction of FI, spin texture on the Fermi surface of 2DEG, and temperature. Our result provides an important foundation for an accurate analysis of the inverse Rashba-Edelstein effect induced by thermal spin injection.

cond-mat.mes-hall↗

arXiv2024

Thermomagnetic Anomalies by Magnonic Criticality in Ultracold Atomic Transport

We investigate thermomagnetic transport in an ultracold atomic system with two ferromagnets linked via a magnetic quantum point contact. Using nonequilibrium Green's function approach, we show a divergence in spin conductance and a slowing down of spin relaxation that manifest in the weak effective-Zeeman-field limit. These anomalous spin dynamics result from the magnonic critical point at which magnons become gapless due to spontaneous magnetization. Our findings unveil untapped dynamics in ultracold atomic systems, opening new avenues in thermomagnetism.

cond-mat.quant-gas↗

arXiv2024

Acousto-magnonic spin Hall effect in honeycomb antiferromagnets

The recently discovered van der Waals antiferromagnets have suffered from the lack of a comprehensive method to study their magnetic properties. Here, we propose a dissipationless magnon spin Hall current driven by surface acoustic waves as a novel probe for such antiferromagnets. Our results pave the way towards mechanical detection and manipulation of the magnetic order in two-dimensional antiferromagnets. Furthermore, they will overcome the difficulties with weak magnetic responses inherent in the use of antiferromagnets and hence provide a building block for future antiferromagnetic spintronics.

cond-mat.mes-hall↗

arXiv2024

Dynamical Majorana Ising spin response in a topological superconductor-magnet hybrid by microwave irradiation

We study a dynamical spin response of surface Majorana modes in a topological superconductor-magnet hybrid under microwave irradiation. We find a method to toggle between dissipative and non-dissipative Majorana Ising spin dynamics by adjusting the external magnetic field angle and the microwave frequency. This reflects the topological nature of the Majorana modes, enhancing the Gilbert damping of the magnet, thereby, providing a detection method for the Majorana Ising spins. Our findings illuminate a magnetic probe for Majorana modes, paving the path to innovative spin devices.

cond-mat.mes-hall↗

arXiv2024

Electric field-induced nonreciprocal spin current due to chiral phonons in chiral-structure superconductors

The recent experiment [R. Nakajima, et al., Nature 613, 479 (2023)] has reported a pair of oppositely polarized spins under an alternating electric current in a superconductor with a chiral structure. However, these behaviors cannot be explained by the conventional Edelstein effect and require a new mechanism. In this Letter, we propose a mechanism of spin current generation under an external electric field due to chiral phonons in a chiral-structure superconductor based on the Bogoliubov de Gennes and the Boltzmann equations. In our mechanism, chiral phonons are induced by electric field due to inversion symmetry breaking and electron-phonon interaction. They work as an effective Zeeman field and hence spin-polarize Bogoliubov quasiparticles in the superconductor. As a result, the spin current carried by quasiparticles flows along the screw axis and shows a quadratic dependence on the electric field at the low-field range, leading to a nonreciprocal spin transport. The spin current also shows a nonmonotonic temperature dependence and has a maximum at around the superconducting transition temperature.

cond-mat.mes-hall↗

arXiv2023

Exploring $^3P_0$ Superfluid in Dilute Spin-Polarized Neutron Matter

We explore the theoretical possibility of $^3P_0$ neutron superfluid in dilute spin-polarized neutron matter, which may be relevant to the crust region of a magnetized neutron star. In such a dilute regime where the neutron Fermi energy is less than 1 MeV, the $^1S_0$ neutron superfluid can be suppressed by a strong magnetic field of the compact star. In the low-energy limit relevant for dilute neutron matter, the $^3P_0$ interaction is stronger than the $^3P_2$ one which is believed to induce the triplet superfluid in the core. We present the ground-state phase diagram of dilute neutron matter with respect to the magnetic field and numerically estimate the critical temperature of the $^3P_0$ neutron superfluid, which is found to exceed $10^7$ K.

nucl-th↗

arXiv2023

Spin Pumping into Carbon Nanotubes

We theoretically study spin pumping from a ferromagnetic insulator (FI) into a carbon nanotube (CNT). By employing the bosonization method, we formulate the Gilbert damping induced by the FI/CNT junction, which can be measured by ferromagnetic resonance. We show that the increase in the Gilbert damping has a temperature dependence characteristic of a Luttinger liquid and is highly sensitive to the Luttinger parameter of the spin sector for a clean interface. We also discuss the experimental relevance of our findings based on numerical estimates, using realistic parameters.

cond-mat.mes-hall↗

arXiv2023

Spin transport between polarized Fermi gases near the ferromagnetic phase transition

We theoretically study the spin current between two polarized Fermi gases with repulsive interactions near the itinerant ferromagnetic phase transition. We consider a two-terminal model where the left reservoir is fixed to be fully polarized while the polarization of the right reservoir is tuned through a fictitious magnetic field defined by the chemical-potential difference between different atomic hyperfine states. We calculate the spectra of the spin-flip susceptibility function, which displays a magnon dispersion emerging from the Stoner continuum at low momentum in the ferromagnetic phase. Based on the spin-flip susceptibility and using Keldysh Green's function formalism, we investigate the spin current induced by quasiparticle and spin-flip tunneling processes, respectively, and show their dependence on the polarization bias between two reservoirs. The one-body (quasiparticle) tunneling demonstrates a linear dependence with respect to the polarization bias. In contrast, the spin-flip process manifests a predominantly cubic dependence on the bias. While indicating an enhanced magnon tunneling in the strong-coupling regime, our results also demonstrate a characteristic behavior around the critical repulsive strength for ferromagnetic phase transition at low temperatures.

cond-mat.quant-gas↗