arXiv subjects

Mamoru Matsuo

Publications and source records attributed to Mamoru Matsuo.

At least 19 recordsLinked to original sources

arXiv2026

Programmable Spin Conversion in Gradient Quantum Matter

We propose programmable spin conversion in ultracold gases as gradient quantum matter, whose spin-dependent self-energy varies in space. Quantum kinetic theory shows that a dissipative self-energy curvature turns a force-driven scalar anisotropy into a spin source with mixed longitudinal-transverse momentum parity. Spin-resolved time-of-flight imaging can reveal a transverse spin texture that changes sign when either the drive or programmed curvature is reversed. Ultracold gases thereby offer a controllable spin source for gradient quantum matter.

cond-mat.quant-gas↗

arXiv2026

Microscopic derivation of the microstretch theory for carbon nanotubes

Twisted carbon nanotubes support phonons involving not only torsion, naturally associated with microrotation, but also radial breathing, which requires a scalar stretch degree of freedom. We derive an effective microstretch theory for these modes starting from nonlinear elasticity on a cylindrical surface. By linearizing the equation of motion around a uniformly twisted equilibrium configuration, we obtain the dynamical matrix for the twisting, longitudinal, and radial-breathing modes. This matrix coincides with that of a one-dimensional microstretch theory, and the corresponding elastic constants are expressed in terms of the Lam\'e constants, the nanotube radius, and the twist rate. The twist generates chiral couplings in the effective theory, which hybridize the three modes and open an anticrossing in the phonon dispersion. These results provide a microscopic basis for the microstretch description of phonons in twisted carbon nanotubes and clarify how structural chirality enters the effective couplings.

cond-mat.mtrl-sci↗

arXiv2026

Quantum Geometric Origin of Hall Viscosity and Nonlocal Hall Conductivity in Lattice Bands

We show that Hall viscosity in lattice bands is governed by a band-projected electric quadrupole encoded within the quantum geometry: Berry curvature sets the projected-coordinate algebra, while the quantum metric determines the quadrupolar spread of a wave packet. The same structure enters the quadratic wave-vector coefficient of the nonlocal Hall conductivity, yielding a lattice viscosity-conductivity relation. In ideal bands, the deviation from the Landau-level form is quantified by Berry curvature fluctuations. Our results establish the nonlocal Hall response as an electrical signature of the quantum geometry underlying Hall viscosity and as a transport diagnostic of geometric idealness.

cond-mat.mes-hall↗

arXiv2026

Microfluidic Actuation by Einstein-de Haas Spin Torque

We propose spin-current microfluidic actuation of a sealed liquid metal. Spin angular momentum injected from Pt contacts enters the liquid as an Einstein-de Haas torque and is converted through micropolar angular-momentum balance into viscous flow without pressure drive, moving walls, magnetic fields, Lorentz forces, or charge flow through the liquid. The dc velocity obeys universal spin-diffusion scaling, and the finite-frequency spin-mechanical admittance resolves viscous momentum diffusion, spin transport, microrotation relaxation, and interface transparency of the liquid-metal channel.

cond-mat.mes-hall↗

arXiv2026

Thermal Spin Polarization Driven by Nuclear Spin-Orbit Coupling in Neutron Star Pasta

We discuss anomalous spin polarization on the surface of nuclear pasta in a neutron star, driven by a nuclear spin-orbit interaction. We present an effective two-band model of surface-localized neutrons near the nuclear pasta. The central point is the emergence of a Rashba-type spin-orbit hybridization generated by the neutron--nucleus spin-orbit force in the presence of the strong density gradient normal to the pasta surface. Starting from a single-particle Hamiltonian with a central potential and a standard nuclear spin-orbit interaction, we show that the surface spin polarization occurs due to the thermal inhomogeneity even in the absence of a magnetic field. Our study links neutron-star physics and solid-state spintronics and would contribute to understanding the interplay between spin dynamics and strong magnetic fields.

nucl-th↗

arXiv2026

Gyromagnetic Quantum Friction in Rayleigh Vorticity Baths

We identify an intrinsic zero-temperature relaxation channel for near-surface spins gyromagnetically coupled to Rayleigh-wave vorticity. This surface-mode contribution requires no thermal phonons, unlike Raman relaxation, and is fixed by Rayleigh vorticity rather than material-specific $g$-factor modulation. The Rayleigh-vorticity bath is super-Ohmic and evanescent with depth, producing field and depth scalings of spin relaxation. These scalings establish shallow spin sensors and hybrid surface-acoustic-wave spin interfaces as detectors of Rayleigh-wave acoustic quantum friction in solids.

cond-mat.mes-hall↗

arXiv2026

Spin Peltier effect in graphene

In this work, we theoretically investigate the spin-Peltier effect in a heterostructure composed of graphene and a ferromagnetic insulator (FI). Using a microscopic formalism based on the characteristic spin-flip scattering length at the graphene/FI interface, we analyze how spin accumulation in graphene gives rise to a temperature difference across the junction. We show that, in the presence of an external magnetic field, the electronic spectrum of graphene is quantized into Landau levels, which strongly modifies the available spin-flip scattering channels. In particular, crossings between Landau levels significantly enhance the spin-flip scattering amplitude, leading to a pronounced amplification of the spin-Peltier response. Our results suggest that measurements of the spin-induced temperature difference in graphene-FI heterostructures can serve as a sensitive probe of discrete electronic energy levels. More broadly, this work provides a theoretical framework for understanding spin-driven thermal effects in hybrid systems combining Dirac materials and magnetic insulators.

cond-mat.mes-hall↗

arXiv2026

Spin Seebeck effect in magnetic junctions with a compensated ferrimagnet

Compensated ferrimagnets enable ferromagnet-like spin transport without net magnetization. We study the spin Seebeck effect in a compensated ferrimagnet/normal-metal junction using a four-sublattice model in which sublattice inequivalence arises from differences in exchange couplings, in contrast to the previously studied anisotropy-based mechanism. Within the nonequilibrium Green's function framework, we show that isotropic magnon splitting generates a robust spin current with a magnitude comparable to that in standard ferromagnetic junctions. We also demonstrate that the spin Seebeck effect vanishes in altermagnet junctions under identical conditions, thereby establishing compensated ferrimagnets as uniquely suited for thermal spin-current generation among magnetically compensated systems. These results provide a theoretical basis for the applications of compensated ferrimagnets with exchange-coupling asymmetry as stray-field-free spin-current sources in spintronic devices.

cond-mat.mes-hall↗

arXiv2026

Generalized continuum theory of phonon angular momentum in crystals

We formulate a generalized continuum theory of phonon angular momentum in crystals by introducing a local SO(3) material frame in addition to the macroscopic displacement field. The local frame represents rotational optical degrees of freedom of the unit cell and brings acoustic displacement modes and optical rotational modes into a common long-wavelength continuum description. In the linearized limit, the co-rotated deformation gradient and the rotational gradient associated with the local material frame recover the Eringen microdeformation and wryness tensors; isotropic micropolar elasticity then appears as a special case. Rotational symmetry and Noether's theorem determine the continuum phonon angular-momentum density, including both the displacement-polarization contribution and the intrinsic microrotation contribution. The theory further identifies the locking limit in which microrotation reduces to lattice vorticity and the improper-symmetry-breaking terms responsible for chiral phonon splitting.

cond-mat.mtrl-sci↗

arXiv2026

Ferromagnetic resonance modulation in topological materials with bulk--boundary coexistence

We extend ferromagnetic resonance (FMR) modulation theory to describe systems in which bulk and boundary states of topological materials coexist, with both appearing at the same energy. As an application of the formulation, we investigate the enhancement of the Gilbert damping constant on the $(110)$ surface of a $d$-wave superconductor where nodal quasiparticles coexist with edge states, which are one-dimensional boundary states, known as surface zero-energy Andreev bound states. We find two characteristic features: a pronounced edge-to-edge excitation peak near zero energy, and an additional edge-to-bulk excitation peak at the superconducting gap energy. We also observe power-law decay at low temperatures and exponential decay at intermediate temperatures in the low-energy regime. These features demonstrate the comparable contributions of the bulk and boundary states to the FMR response. Our theory provides a broadly applicable framework for the analysis of topological materials.

cond-mat.mes-hall↗

arXiv2026

Torsional oscillation of carbon nanotubes driven by electron spins

We theoretically investigate the current-induced excitation of torsional vibrations in a suspended carbon nanotube (CNT) quantum dot. By considering a CNT clamped between half-metallic ferromagnetic electrodes with an antiparallel magnetization configuration, we demonstrate that the spin-rotation coupling enables the transfer of angular momentum from electron spins to the mechanical torsional mode under a constant source-drain voltage. Using a master-equation approach to analyze the coupled dynamics of the dot levels and a quantized torsional oscillator, we evaluate the steady-state current and phonon distribution. We find that when the Zeeman splitting matches the torsional phonon energy, the system exhibits a sharp resonant behavior in the current, accompanied by a significant increase in the phonon population. Our estimates for realistic device parameters indicate that this spin-driven mechanism can drive CNT torsional vibrations with detectable amplitudes. This work provides a theoretical basis for current-controlled actuation of nanoelectromechanical systems via the spin angular momentum of electrons.

cond-mat.mes-hall↗

arXiv2026

Probing valley quantum oscillations via the spin Seebeck effect in transition metal dichalcogenide/ferromagnet hybrids

We theoretically investigate spin-valley-locked tunneling transport in a transition-metal dichalcogenide/ferromagnetic-insulator heterostructure under a perpendicular magnetic field, driven by the spin Seebeck effect. We demonstrate that spin-valley coupling together with the magnetic-field-induced valley-asymmetric Landau-level structure enables the generation of a valley-polarized spin current from valley-selective spin excitation. We compare the spin current and the valley-polarized spin current in the conduction and valence bands and clarify their distinct microscopic origins. We predict pronounced quantum oscillations of the valley-polarized spin current, providing a clear experimental signature of quantized valley states.

cond-mat.mes-hall↗

arXiv2025

Valley Hall Viscosity in Gapped Graphene with and without a Magnetic Field

Hall viscosity is conventionally defined through the stress response to time-dependent strain, a perturbation that is difficult to implement in solid-state experiments. We formulate a related viscoelastic response to static, spatially inhomogeneous electric fields and compare it with the strain-based response. For gapped graphene in a perpendicular magnetic field, the two formulations give the same Landau-level response, whose Hall viscosity is asymmetric between the two valleys. At zero magnetic field, a valley-even quantum-metric coefficient combines with the valley-odd Hall conductivity to produce equal and opposite valley-resolved responses; global time-reversal symmetry therefore forces the net Hall viscosity to vanish. In an insulating state, exact particle--hole symmetry eliminates this zero-field response, whereas particle--hole-symmetry breaking generates a cutoff-dependent geometric contribution from the occupied Fermi sea. These results connect valley-dependent viscoelasticity with electromagnetic response in gapped Dirac materials and clarify the conditions under which a valley Hall viscosity can arise.

cond-mat.mes-hall↗

arXiv2025

Quantum oscillations of valley current driven by microwave irradiation in transition-metal dichalcogenide/ferromagnet hybrids

We theoretically study spin and valley transport in a transition-metal dichalcogenide(TMDC)/ferromagnet heterostructure under a perpendicular magnetic field. We find that microwave-driven spin pumping induces a valley-selective spin excitation, a direct consequence of the valley-asymmetric Landau levels in the TMDC conduction band. This process generates a pure valley current which, as our central finding, exhibits pronounced quantum oscillations as a function of chemical potential. These oscillations provide a definitive experimental signature of the quantized valley states and establish another pathway to interface spintronics and valleytronics.

cond-mat.mes-hall↗

arXiv2025

Spin Current Generation Controlled by the N\'{e}el State in a Compensated Ferrimagnet

Compensated ferrimagnets, which break sublattice and time-reversal symmetries in the ground state, exhibit an isotropic ferromagnet-like spin splitting despite a vanishing net magnetization, in contrast to altermagnets with momentum-dependent spin splitting. We investigate how isotropic spin splitting manifests in spin transport by analyzing the spin Seebeck effect and spin pumping in a junction between a compensated ferrimagnet and a normal metal. We show that compensated ferrimagnets generate a sizable spin Seebeck signal, with a sign that can be reversed by switching between the two N\'{e}el states. Furthermore, we demonstrate that spin pumping exhibits a N\'{e}el-state-dependent resonance splitting, which is absent in conventional antiferromagnets. These results identify spin pumping as a natural readout mechanism for compensated ferrimagnets and establish them as promising magnetization-free building blocks for spintronic memory devices.

cond-mat.mes-hall↗

arXiv2025

Theory of spin Seebeck effect activated by acoustic chiral phonons

We theoretically explore the generation of spin current driven by a temperature gradient in a junction between a chiral insulator and a normal metal. Based on the gyromagnetic response induced by microscopic acoustic-phonon-mediated lattice rotation, we derive a formula for the spin current when a finite temperature difference is imposed between two ends of the sample. We clarify how the phonon-mediated spin current depends on the sample geometry, the thermal conductivity, the heat conductance at the interface, and the average temperature. Our formulation provides a microscopic foundation for the chiral-phonon-activated spin Seebeck effect without relying on magnetism or spin-orbit interactions.

cond-mat.mes-hall↗

arXiv2025

Spin Pumping into two-dimensional systems

In this review, we present recent theoretical developments on spin transport phenomena probed by ferromagnetic resonance (FMR) modulation in two-dimensional systems coupled to magnetic materials. We first address FMR linewidth enhancements induced by spin pumping at interfaces, emphasizing their potential as sensitive probes of superconducting pairing symmetries in two-dimensional superconductors. We then examine FMR modulation due to spin pumping into two-dimensional electron gases formed in semiconductor heterostructures, where the interplay of Rashba and Dresselhaus spin-orbit interactions enables gate-controlled spin transport and persistent spin textures. Finally, we investigate spin pumping in monolayer transition-metal dichalcogenides, where spin-valley coupling and Berry curvature effects lead to valley-selective spin excitations and a spin-current Hall effect. These developments demonstrate that the spin pumping technique provides a versatile tool for probing spin transport and spin-dependent phenomena in low-dimensional systems, offering a basis for future spintronics applications.

cond-mat.mes-hall↗

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↗