A5003204394- Advanced Condensed Matter Physics
- Topological Materials and Phenomena
- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Magnetic properties of thin films
- Graphene research and applications
- Magnetic and transport properties of perovskites and related materials
- Theoretical and Computational Physics
- Multiferroics and related materials
- Electric Motor Design and Analysis
- 2D Materials and Applications
- Magnetic Bearings and Levitation Dynamics
- Electronic and Structural Properties of Oxides
- Quantum many-body systems
- Magnetic Field Sensors Techniques
- Spectroscopy and Quantum Chemical Studies
- Magnetic Properties and Applications
- Rare-earth and actinide compounds
- Nuclear materials and radiation effects
- Advanced Thermodynamics and Statistical Mechanics
- Cold Atom Physics and Bose-Einstein Condensates
- Semiconductor Quantum Structures and Devices
- Solid-state spectroscopy and crystallography
- Smart Grid and Power Systems
- Geomagnetism and Paleomagnetism Studies
Tokyo Institute of Technology
1994-2024
Institute of Science Tokyo
2024
Shanghai Institute for Science of Science
2024
Massachusetts Institute of Technology
2021-2022
The University of Tokyo
2012-2021
Okayama University
2019-2021
Toshiba (Japan)
1986-2020
Keihin (Japan)
2015-2020
Showa General Hospital
2020
Toho University
2019
Coupling different physical properties is a fascinating subject of physics. Already well-known are the multiferroics which show ferroelectrics and magnets. But ferroelectricity by itself also entails bulk photovoltaic effect, light-matter interaction generates dc currents. Here we propose magnetic photogalvanic effect that couples magnetism to interaction. This phenomenon emerges from $\mathbf{k}$ $\mathbf{-k}$ symmetry-breaking in band structure does not require static polarization. It...
A new mechanism of skew scattering and anomalous Hall effect due to the spin chirality fluctuation is proposed theoretically.
We report a nonmonotonic magnetic field dependence of the anomalous Hall effect due to change Zeeman splitting.
Using first-principles calculations, we investigate the photogalvanic effect in Weyl semimetal material TaAs. We find colossal photocurrents caused by points band structuure a wide range of laser frequency. Our calculations reveal that photocurrent is predominantly contributed three-band transition from occupied to empty via an intermediate away cone, for excitations both linearly and circularly polarized lights. Therefore, it significant sum over all transitions considering full set Bloch...
Abstract The electrical Hall effect can be significantly enhanced through the interplay of conduction electrons with magnetism, which is known as anomalous (AHE). Whereas mechanism related to band topology has been intensively studied towards energy efficient electronics, those electron scattering have received limited attention. Here we report observation giant AHE electron-scattering origin in a chiral magnet MnGe thin film. conductivity and angle, respectively, reach $$40,000$$ <mml:math...
An idea is proposed for realizing a fully spin-polarized Dirac semimetal in frustrated itinerant magnets. We show that electrons on triangular lattice exhibit the cone dispersion with half-metallic behavior presence of three-sublattice ferrimagnetic order. The nodes have same structure as those graphene. By variational calculation and Monte Carlo simulation, we demonstrate order node spontaneously emerges simple Kondo model Ising anisotropy. realization will be beneficial spintronics...
Topological quantum states of matter, characterized by geometrical features electronic band structures, have been extensively studied. Among them, the topological state with magnetic order remains elusive because a scarce number examples. Here we present experimental observations proving that pyrochlore iridate, when electronically tuned, can be Weyl semimetal as predicted recent theories. We observe sizable spontaneous Hall conductivity minimal magnetization only within few Kelvin below...
The photovoltaic effect due to the adiabatic quantum phase in noncentrosymmetric Weyl semimetals is studied. We particularly focus on case which an external ac electric field applied. By considering a generalized Hamiltonian with nonlinear terms, we show that photocurrent induced by circularly, rather than linearly, polarized light. This current can be understood as emergent electromagnetic induction momentum space; node magnetic monopole space, circular motion of induces field. result...
By considering an extended double-exchange model with spin-orbit coupling (SOC), we derive a general form of the Berry phase $\ensuremath{\gamma}$ that electrons pick up when moving around closed loop. This generalizes well-known result valid for SU(2) invariant systems, $\ensuremath{\gamma}=\mathrm{\ensuremath{\Omega}}/2$, where $\mathrm{\ensuremath{\Omega}}$ is solid angle subtended by local magnetic moments enclosed The demonstrates collinear and coplanar textures can also induce...
The non-collinear spin configurations cause many nontrivial phenomena related to the Berry phase. They are described by vector chirality $\chi_{ij} ={\bf S}_i\times{\bf S}_j$ or scalar $\chi_{ijk}=({\bf S}_i \times {\bf S}_j) \cdot S}_k$, which current and effective magnetic field, respectively. leads topological Hall effect in metals, while ferroelectricity of origin, i.e., multiferroics insulators. However, role conducting systems has not yet elucidated. Here we show theoretically that...
Abstract The thermal Hall effect in magnetic insulators has been considered a powerful method for examining the topological nature of charge-neutral quasiparticles such as magnons. Yet, unlike kagome system, triangular lattice received less attention studying because scalar spin chirality cancels out between adjacent triangles. However, cancellation cannot be perfect if is distorted. Here, we report that trimerized multiferroic hexagonal manganite YMnO 3 produces highly unusual under an...
Shift current---a photocurrent induced by light irradiating noncentrosymmetric materials in the absence of any bias voltage or built-in electric field---is one mechanisms so-called bulk photovoltaic effect. It has been traditionally described as a nonlinear optical response periodic solids to continuous wave using perturbative formula, which is linear intensity and involves Berry connection describing shift center mass position Wannier function associated with transition between valence...
A mechanism for the phonon Hall effect (PHE) in nonmagnetic insulators under an external magnetic field is theoretically studied. PHE known (para)magnetic compounds, where moments and spin-orbit interaction play essential role. In sharp contrast, we here discuss that also occurs band subject to field. We find a correction Born-Oppenheimer approximation gives rise Raman-type between phonons; this Berry curvature of band. This results finite thermal conductivity ${\ensuremath{\kappa}}_{H}$...
Skew scattering---an asymmetric scattering of electrons by impurities---is one the major mechanisms causing anomalous/spin Hall effects. Although many microscopic for skew are known, angle anomalous effect these is often small, typically $\ensuremath{\theta}=0.{1}^{\ensuremath{\circ}}\ensuremath{-}{1}^{\ensuremath{\circ}}$. In this paper, we study three-spin clusters focusing on strong Kondo-coupling regime. Using a $T$-matrix formalism, calculate probability arbitrary strength Kondo...
Here we study nonmonotonic features which appear both in magnetoresistivity and anomalous Hall resistivity during the simple magnetization process, by systematically measuring type-II magnetic Weyl semimetal EuCd$_2$Sb$_2$ films over a wide carrier density range. We find that positive hump can be explained as manifestation of field-linear term generalized magnetoconductivity formula including Berry curvature. As also confirmed model calculation, negative pronounced near point energy case...
Understanding electron-phonon interactions is fundamentally important and has crucial implications for device applications. However, in twisted bilayer graphene near the magic angle, this understanding currently lacking. Here, we study coupling using time- frequency-resolved photovoltage measurements as direct complementary probes of phonon-mediated hot-electron cooling. We find a remarkable speedup cooling angle: The time few picoseconds from room temperature down to 5 kelvin, whereas...
The non-monotonic temperature dependence and sign reversal of chirality-related anomalous Hall effect in highly conductive metals are studied. Through the analysis scattering rate, we find that non-monotonicity have two major origins: (1) competition between contribution from short-range long-range spin correlations (2) correlation high field. former mechanism gives rise to a wide range electron density and, some cases, resistivity as decreases. On other hand, latter is responsible for...
Recent observation of anomalous Hall effect (AHE) induced by magnetic field or spin magnetization lying in the deflection plane has sparked interest diverse mechanisms for inducing vector component perpendicular to applied field. Such off-diagonal coupling, which is strictly constrained symmetry system, provides new degrees freedom engineering responses. However, spontaneous response as extensively studied out-of-plane AHE remains unexplored. Here we elucidate in-plane a typical...
We present a mechanism of resistivity minimum in conduction electron systems coupled with localized moments, which is distinguished from the Kondo effect. Instead spin-flip process effect, electrons are elastically scattered by local spin correlations evolve particular way under geometrical frustration as decreasing temperature. This demonstrated cellular dynamical mean-field theory for spin-ice-type lattice model on pyrochlore lattice. Peculiar temperature dependences resistivity, specific...
We study magnetism of a fcc lattice spin model with tetragonal distortions, general exotic directional magnetic interactions allowed by symmetry. consider two models, corresponding to uniform distortion, or two-sublattice screw axis. establish their low-temperature phase diagrams in the semiclassical limit using classical optimization and consideration fluctuations both analytically Monte Carlo simulation. found that order-by-disorder exchange-anisotropy mechanisms favor...
We study the quantum mechanics of magnetic skyrmions in vicinity skyrmion-crystal to ferromagnet phase boundary two-dimensional magnets. show that skyrmion excitation has an energy dispersion splits into multiple bands due combination magnus force and underlying lattice. Condensation can give rise intermediate between crystal ferromagnet: a liquid, which are not spatially localized. critical behavior depends on spin size $S$ topological number skyrmion. Experimental signatures inelastic...
The authors have investigated the relation between circuit conditions and chopping current values of various types breakers, including MOCB(Minimum Oil CB), VCB(Vacuum ABCB (Air Blast CB) GCB (SF6 Puffer CB). Excepting VCB, each breaker increases with increase parallel capacitance to breaker, but it decreases when a series resistance is connected this capacitance. Concerning MOCB, GCB, was found that phenomena just before quite resemble other, while as for differs from others completely....