A5076083635- Physics of Superconductivity and Magnetism
- Terahertz technology and applications
- Topological Materials and Phenomena
- Magnetic and transport properties of perovskites and related materials
- Rare-earth and actinide compounds
- Acoustic Wave Resonator Technologies
- Iron-based superconductors research
- Solid-state spectroscopy and crystallography
- Photonic and Optical Devices
- Quantum and electron transport phenomena
- Multiferroics and related materials
- Advanced Condensed Matter Physics
- Magnetic properties of thin films
- Bioactive Compounds and Antitumor Agents
- Organic and Molecular Conductors Research
- Microbial Natural Products and Biosynthesis
- Shape Memory Alloy Transformations
- Photorefractive and Nonlinear Optics
- Semiconductor Quantum Structures and Devices
- Perovskite Materials and Applications
- Advanced Semiconductor Detectors and Materials
- Thermal properties of materials
- Phenothiazines and Benzothiazines Synthesis and Activities
- Corporate Taxation and Avoidance
- Internet of Things and Social Network Interactions
The University of Tokyo
2014-2025
Tohoku University
2022
Kyushu Institute of Technology
2019-2021
Kwansei Gakuin University
2021
Tokyo University of Science
2016
Waseda University
2009
Nipro (Japan)
2009
Shinshu University
1992
Abstract Applying a magnetic field to solid changes its thermal-transport properties. Although such magneto-thermal-transport phenomena are usually small effects, giant magneto-thermal resistance has recently been observed in spintronic materials and superconductors, opening up new possibilities thermal management technologies. However, the conductivity conventionally only when is applied due absence of nonvolatility, which limits potential applications switching devices. Here, we report...
Solids with competing interactions often undergo complex phase transitions a variety of long-periodic modulations. Among such transition, devil's staircase is the most phenomenon, and for it, CeSb famous material, where number distinct phases magnetostructures sequentially appear below Neel temperature. An evolution low-energy electronic structure going through special interest, which has, however, been elusive so far despite 40-years intense researches. Here we use bulk-sensitive...
In electronic-type ferroelectrics, where dipole moments produced by the variations of electron configurations are aligned, polarization is expected to be rapidly controlled electric fields. Such a feature can used for high-speed electric-switching and memory devices. Electronic-type ferroelectrics include charge degrees freedom, so that they sometimes conductive, complicating dielectric measurements. This makes difficult exploration understanding their ferroelectric nature. Here, we show...
Abstract C 4 plants are believed to have evolved from 3 through various –C intermediate stages in which a photorespiration‐dependent CO 2 concentration system known as photosynthesis operates. Genes involved the cycle were thought be recruited orthologs present species and developed cell‐specific expression during evolution. To understand process of establishing photosynthesis, we performed whole‐genome sequencing investigated mesophyll‐ or bundle‐sheath‐cell‐specific localization...
Quantized vortices in type-II superconductors provide insights into the mechanisms of superconductivity. However, generation antivortices, characterized by magnetization antiparallel to external magnetic field, remains less understood. In this study, we investigate Sn-Pb solder, a superconductor with phase-separated Sn and Pb phases, report observation both antivortices. Scanning SQUID (superconducting quantum interference device) microscopy revealed presence while magneto-optical imaging...
There are several strategies to discover new superconductors. Growing materials and applying high pressures can be the classic ways since superconductivity was found. Also, chemical processing, such as annealing, is another way induce in a non-superconducting material. Here, we show processing effects material, sulfur-substituted FeTe. It has been known that S-substituted FeTe induced by O$_2$ annealing. We revealed hydrochloric acid etching vacuum annealing for O$_2$-annealed samples made...
Among the thirty-two crystallographic point groups, 432 is only one that lacks an inversion center but does not exhibit piezoelectricity. A gyroidal structure belongs to group and shows characteristic physical properties attributed its distinctive strong isotropic network. Here, we investigate a cobalt oxalate metal-organic framework (MOF) with disordered orientations of SO4 tetrahedra. Synchrotron X-ray diffraction experiments using single crystal reveal cubic-to-cubic structural phase...
Skyrmions in noncentrosymmetric materials are believed to occur due the Dzyaloshinskii-Moriya interaction. By contrast, skyrmion formation mechanism centrosymmetric remains elusive. Here, we reveal intrinsic electronic structure of GdRu 2 Si by selectively measuring magnetic domains using angle-resolved photoemission spectroscopy (ARPES). We found robust Fermi surface (FS) nesting, consistent with modulation q -vector detected previous resonant x-ray scattering measurements. The pseudogap...
The manipulation of the valley degree freedom can boost technological development novel functional devices based on valleytronics. current mainstream platform for valleytronics is to produce a monolayer with inversion asymmetry, in which strain-band engineering through substrates serve improve performance valley-based devices. However, pinpointing effective role strain inevitable precise design desired structure. Here, we demonstrate charge transport under continuously controllable external...
We report the terahertz radiation in polar and ferrimagnetic insulating oxide LiFe5O8 upon irradiation of a femtosecond laser pulse at room temperature. By resonant optical excitation an originally spin-forbidden d–d transition Fe3+ ions, we observed emission waves, which is attributable to magnetic-dipole originating from light-induced subpicosecond magnetization modulation. mapping out successfully visualized vector images in-plane magnetic domains fields. The terahertz-radiation imaging...
We report on the emission of terahertz radiation by irradiation femtosecond laser pulses in non-centrosymmetric paraelectric and ferroelectric phases Co3B7O13I boracite. The generation waves both is caused optical rectification via a second-order nonlinear effect. In phase, we successfully visualized domains analyzing polarization state wave radiated from crystal. large area crystal (∼500 × 500 µm2), observed vector was tilted directions spontaneous polarization, i.e., , cubic setting, which...
Nonlinear electric transport and switching to a negative resistance state are typical electric-field-induced phenomena in correlated electron materials, while their mechanisms generally difficult solve. In the present study, we apply terahertz-radiation imaging method an organic molecular ferroelectric, \ensuremath{\alpha}-type bis(ethylenedithio)tetrathiafulvalene iodide salt, investigate nature of its phenomenon. When is produced, ferroelectric order melted elongated region with width...
Abstract Hysteretic behaviour accompanies any first-order phase transition, forming a basis for many applications. However, its quantitative understanding remains challenging, and even qualitative of pronounced hysteresis broadening at low temperature, which is often observed in magnetic-field-induced transition materials, unclear. Here, we show that such emerges if the phase-front velocity during exhibits an activated as function both temperature magnetic field. This demonstrated by using...
Abstract Bulk bismuth has a complex Landau spectrum. The small effective masses and the large g-factors are anisotropic. chemical potential drifts at high magnetic fields. Moreover, twin boundaries further complexify interpretation of data by producing extra anomalies in extreme quantum limit. Here, we present study angle dependence magnetoresistance up to 65 T complemented with Nernst, ultrasound, magneto-optic data. All observed can be explained single-particle picture sample consisting...
Terahertz radiation by optical rectification has been observed at room temperature in a hydrogen-bonded organic molecular ferroelectric crystal, 2-phenyl malondialdehyde (PhMDA). The radiated electromagnetic wave consisted of single-cycle terahertz pulse with temporal width ∼0.5 ps. amplitude divided the sample thickness PhMDA was nearly equivalent to that typical emitter ZnTe. This is attributable long coherence length range 130–800 µm for from PhMDA. We also discussed possibility as terms...
In the extreme quantum-limit states under high magnetic fields, enhanced electronic correlation effects can stabilize anomalous quantum states. Using band-tuning with a field, we realized spin-polarized state in field-induced semimetallic phase of topological insulator ${\mathrm{Bi}}_{1\text{\ensuremath{-}}x}{\mathrm{Sb}}_{x}$. Further increase field injects more electrons and holes to this results an unexpected reentrant state. A single-particle picture cannot explain state, reminiscent...
The spin-splitting energy bands induced by the relativistic spin-orbit interaction in solids provide a new opportunity to manipulate spin-polarized electrons on sub-picosecond time scale. Here, we report one such example bulk Rashba-type polar semiconductor BiTeBr. Strong terahertz electromagnetic waves are emitted after resonant excitation of interband transition between with femtosecond laser pulse circularly polarized. phase is reversed switching circular polarization. This suggests that...
Terahertz lights are usually generated through the optical rectification process within a femtosecond laser pulse in noncentrosymmetric materials. Here, we report new generation mechanism of terahertz based upon photoinduced phase transition, which an electronic structure is rapidly changed by photoirradiation. When ferroelectric organic molecular compound, tetrathiafulvalene-p-chloranil, excited pulse, ionic-to-neutral transition driven and simultaneously strong radiation produced. By...
We performed terahertz-pulse-pump second-harmonic-generation (SHG)-probe and optical-reflectivity-probe measurements on a single crystal of displacive-type ferroelectric, BiFeO3, to achieve an ultrafast control the optical response by terahertz pulse. By application pulse with amplitude about 200 kV/cm along polarization direction, SHG intensity was modulated completely electric-field waveform, suggesting that relevant ionic motions are faster than time resolution ∼130 fs measurement as well...
We have developed a long-distance polarizing microscope system combined with solenoid-type superconducting magnet. By inserting an infinity-corrected objective lens into the magnet, direct or images are observed in magnetic fields of up to 12 T at various temperatures down 2 K. Through magneto-optical measurements transmission geometry, local magnetization process transparent magnet is evaluated areas 10 × µm2. This enables simultaneous other physical properties over wide range and fields....
Single crystals of the triangular lattice antiferromagnet (TLAF) ${\mathrm{Ca}}_{3}{\mathrm{NiNb}}_{2}{\mathrm{O}}_{9}$ and its nonmagnetic analog ${\mathrm{Ca}}_{3}{\mathrm{MgNb}}_{2}{\mathrm{O}}_{9}$ are grown using four-mirror optical floating-zone furnace. By varying growth conditions, two types mm-sized obtained: monoclinic form where ${\mathrm{Ni}}^{2+}$ ${\mathrm{Nb}}^{5+}$ exhibits 1:2 ordering Ni ions (spin 1) arranged on a lattice, orthorhombic ${\mathrm{CaBO}}_{3}$ B site is...