A5035458528- Topological Materials and Phenomena
- Structural Load-Bearing Analysis
- Structural Engineering and Vibration Analysis
- Graphene research and applications
- Magnetic properties of thin films
- Structural Behavior of Reinforced Concrete
- 2D Materials and Applications
- Quantum and electron transport phenomena
- Heusler alloys: electronic and magnetic properties
- Seismic Performance and Analysis
- Electronic and Structural Properties of Oxides
- Structural Analysis and Optimization
- Fatigue and fracture mechanics
- Ferroelectric and Piezoelectric Materials
- Advanced Condensed Matter Physics
- Advanced Thermoelectric Materials and Devices
- Magnetic and transport properties of perovskites and related materials
- Structural Response to Dynamic Loads
- Seismic and Structural Analysis of Tall Buildings
- Semiconductor materials and devices
- Urban and spatial planning
- Vibration Control and Rheological Fluids
- Structural Health Monitoring Techniques
- Metal Forming Simulation Techniques
- Fire effects on concrete materials
Kyoto University
2011-2025
The University of Tokyo
2008-2024
Kyoto Katsura Hospital
2023-2024
Kanazawa University
2017-2020
RIKEN Center for Emergent Matter Science
2020
Tokyo Denki University
2012-2018
Tokyo Metropolitan University
1996-2012
Japan Society for the Promotion of Science
2011
Shinshu University
2008
Architectural Institute of Japan
2004
Abstract The Weyl semimetal (WSM), which hosts pairs of points and accompanying Berry curvature in momentum space near Fermi level, is expected to exhibit novel electromagnetic phenomena. Although the large optical/electronic responses such as nonlinear optical effects intrinsic anomalous Hall effect (AHE) have recently been demonstrated indeed, conclusive evidence for their topological origins has remained elusive. Here, we report gigantic magneto-optical (MO) response arising from...
Magnetic Weyl semimetals attract considerable interest not only for their topological quantum phenomena but also as an emerging materials class realizing anomalous Hall effect in the two-dimensional limit. A shandite compound Co3Sn2S2 with layered kagome-lattices is one such material, where vigorous efforts have been devoted to synthesize crystal. Here, we report a synthesis of thin flakes thickness 250 nm by chemical vapor transport method. We find that this facile bottom-up approach allows...
Anomalous Nernst effect (ANE), converting a heat flow to transverse electric voltage, originates from the Berry phase of electronic wave function near Fermi energy EF. Thus, ANE provides sensitive probe detect topological state that produces large curvature. In addition, magnet exhibits using low-cost and safe elements will be useful develop novel harvesting technology. Here, we report our observation high exceeding 3 microvolts per kelvin above room temperature in kagome ferromagnet Fe3Sn...
We elucidate the transport properties and electronic structures of distorted rutile-type WO2. Electrical resistivity Hall effect measurements high-quality single crystals revealed property characteristics topological materials; these included an extremely large magnetoresistance 13 200% (2 K 9 T) a very high carrier mobility 25 700 cm2 V−1 s−1 (5 K). First-principles calculations Dirac nodal lines (DNLs) near Fermi energy in structure when spin–orbit interactions (SOIs) were absent. Although...
The electronic structure of compensated antiferromagnets (CAF) creates large functional responses, reminiscent ferromagnets and suitable for data storage readout, despite (nearly) net-zero spontaneous magnetization. Many experimental signatures CAF - such as giant thermoelectric Nernst effects should be enhanced when two or more bands are nearly degenerate in vicinity the Fermi energy. Here, we report a zero-field, effect >1 μV/K CoNb3S6 its tiny net magnetization ~2 milli − μB. As drivers...
Motivated by the recent discovery of a large anomalous Nernst effect in Co$_2$MnGa, Fe$_3X$ ($X$=Al, Ga) and Co$_3$Sn$_2$S$_2$, we performed first-principles study to clarify origin enhancement transverse thermoelectric conductivity ($\alpha_{ij}$) these ferromagnets. The intrinsic contribution $\alpha_{ij}$ can be understood terms Berry curvature ($\Omega$) around Fermi level, $\Omega$ is singularly along nodal lines (which are gapless absence spin-orbit coupling) Brillouin zone. We find...
We study the mechanism of exceptionally large anomalous Hall effect (AHE) in noncentrosymmetric antiferromagnet $\mathrm{Co}{\mathrm{Nb}}_{3}{\mathrm{S}}_{6}$ by angle-resolved photoemission spectroscopy (ARPES) and magnetotransport measurements. From ARPES measurements its family compounds ($\mathrm{Fe}{\mathrm{Nb}}_{3}{\mathrm{S}}_{6}$ $\mathrm{Ni}{\mathrm{Nb}}_{3}{\mathrm{S}}_{6}$), we find a band dispersion unique to Co intercalation existing near Fermi level. further demonstrate that...
Abstract Recent discoveries of the topological magnets have opened a new path for developing much simpler thermoelectric conversion module using anomalous Nernst effect (ANE). To accelerate such innovation, it is essential to design materials suitable industrial processes, and thus high‐ANE polycrystalline material has been highly desired. Recently, giant room‐temperature ANE reported in single crystals ferromagnet Fe 3 Ga. Owning its cubic structure, Hall are isotropic. These properties...
We implemented a finite-difference algorithm for computing anomalous Hall and Nernst conductivity. Based on the expression to evaluate Berry curvature in an insulating system [J. Phys. Soc. Jpn. 74, 1674 (2005)], we extended methods metallic system. calculated conductivity two-dimensional ferromagnetic material ${\mathrm{FeCl}}_{2}$ three-dimensional transition-metals bcc-Fe, hcp-Co, fcc-Ni. Our results are comparable previously reported computed by Kubo formula or Wannier representation. To...
The emergence of nontrivial topological order in condensed matter has been attracting a great deal attention owing to its promising technological applications novel functional nanodevices. In ferroelectrics, the realization polar at an ultimately small scale is extremely challenging due lack chiral interaction and critical size ferroelectricity. Here, we break through these limitations demonstrate that ultimate atomic-scale skyrmion meron (∼2 nm) can be induced by engineering oxygen...
Half-Heusler (HH) alloys are an important and well-studied class of thermoelectric, magnetic, spintronic materials. However, few studies have reported on thermal conductivity magnetic HH alloys. In this study, we performed first-principles calculation the thermoelectric properties a alloy CoMnSb. The lattice CoMnSb was found to be smaller than typical nonmagnetic (CoTiSb, CoZrSb). reason for small group velocity relaxation time acoustic phonons. Moreover, estimated electronic power factor,...
We performed first-principles simulations to elucidate the transverse thermoelectric effect (anomalous Nernst effect) of half-metallic FeCl2 monolayer. analyzed its thermoelectricity based on semiclassical transport theory including Berry curvature and found that carrier-doping induced a large anomalous was ∼6.65 μV/K at 100 K if we assumed 10 fs for relaxation time. This magnitude originates in K-point hexagonal Brillouin zone. These results suggest two-dimensional ferromagnetic materials...
Brittle fracture of a covalent material is ultimately governed by the strength electronic bonds. Recently, attempts have been made to alter mechanical properties including excess electron/hole doping. However, underlying mechanics/mechanism how these doped electrons/holes interact with bond and changes its yet be revealed. Here, we perform first-principles density-functional theory calculations clarify effect on bonding Si. We demonstrate that Si decreases or increases monotonically in...
The transverse thermoelectric effect based on the anomalous Nernst (ANE) has attracted attention, especially for and spintronic applications. Fe3X (X = Ga, Al) is known to exhibit a large ANE at room temperature owing topological electronic band structure so-called nodal web. Here, we systematically investigate in polycrystalline Fe3Ga1−xAlx Fe3Al1−xSix. Despite significant chemical substitutions, very robust feature of −Syx∼ 5.7 μ V/K found (0≲x≲0.6), exhibiting striking x independent web...
A large intrinsic anomalous Hall effect (AHE) originating in the Berry curvature has attracted growing attention for potential applications. The recently proposed magnetic Weyl semimetal ${\mathrm{EuCd}}_{2}{\mathrm{Sb}}_{2}$ provides an excellent platform controlling AHE because it only hosts a Weyl-point-related band structure near Fermi energy. Here, we report fabrication of single-crystalline films and control their by film technique. As also analyzed first-principles calculations...
Abstract Geometrical aspects of electronic states in condensed matter have led to the experimental realization enhanced electromagnetic phenomena, as exemplified by giant anomalous Hall effect (AHE) topological semimetals. However, guideline large AHE is still immature due lack profound understanding sources Berry curvature actual structures; main focus has concentrated only on band crossings near Fermi level. Here, we show that and flat bands cooperatively produce intrinsic ferromagnetic...
The electronic structure of compensated antiferromagnets (CAF) has drawn attention for its ability to create large responses, reminiscent ferromagnets and suitable data storage readout, despite (nearly) net-zero spontaneous magnetization. Many the striking experimental signatures predicted CAF, such as giant thermoelectric Nernst effects, are enhanced when two or more bands nearly degenerate in vicinity Fermi energy. Here, we use electric transport experiments study layered, chiral metal...