A5019407261- Topological Materials and Phenomena
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- Graphene research and applications
- Magnetic properties of thin films
- Magnetic and transport properties of perovskites and related materials
- 2D Materials and Applications
- Electronic and Structural Properties of Oxides
- Quantum many-body systems
- Photorefractive and Nonlinear Optics
- Quantum and electron transport phenomena
- Adipokines, Inflammation, and Metabolic Diseases
- Adipose Tissue and Metabolism
- Superconductivity in MgB2 and Alloys
- Iron-based superconductors research
- Rare-earth and actinide compounds
- Theoretical and Computational Physics
- Geomagnetism and Paleomagnetism Studies
- Regulation of Appetite and Obesity
- Diamond and Carbon-based Materials Research
- Semiconductor materials and devices
- Terahertz technology and applications
- Ferroelectric and Negative Capacitance Devices
- Quantum Mechanics and Non-Hermitian Physics
- Magnetic Bearings and Levitation Dynamics
Kyoto Sangyo University
2016-2024
Kobe University
2023
Osaka University
2007-2016
Osaka Research Institute of Industrial Science and Technology
2008-2016
The University of Tokyo
2013
Central Research Institute of Electric Power Industry
2000-2009
Nippon Steel (Japan)
2008
Shibaura Institute of Technology
2006-2008
Takara (Japan)
2004-2005
Nara Institute of Science and Technology
2004-2005
Fat tissue produces a variety of secreted proteins (adipocytokines) with important roles in metabolism. We isolated newly identified adipocytokine, visfatin, that is highly enriched the visceral fat both humans and mice whose expression level plasma increases during development obesity. Visfatin corresponds to protein previously as pre–B cell colony-enhancing factor (PBEF), 52-kilodalton cytokine expressed lymphocytes. exerted insulin-mimetic effects cultured cells lowered glucose levels...
Obesity is linked to a variety of metabolic disorders, such as insulin resistance and atherosclerosis. Dysregulated production fat-derived secretory factors, adipocytokines, partly responsible for obesity-linked disorders. However, the mechanistic role obesity per se adipocytokine dysregulation has not been fully elucidated. Here, we show that adipose tissue obese mice hypoxic local hypoxia dysregulates adipocytokines. Tissue was confirmed by an exogenous marker, pimonidazole, elevated...
Topological insulators are predicted to present interesting surface transport phenomena but their experimental studies have been hindered by a metallic bulk conduction that overwhelms the transport. We show topological insulator ${\text{Bi}}_{2}{\text{Te}}_{2}\text{Se}$ presents high resistivity exceeding $1\text{ }\ensuremath{\Omega}\text{ }\text{cm}$ and variable-range hopping behavior, yet Shubnikov-de Haas oscillations coming from state. Furthermore, we able clarify both channels,...
A topological superconductor (TSC) is characterized by the topologically protected gapless surface state that essentially an Andreev bound consisting of Majorana fermions. While a TSC has not yet been discovered, doped insulator ${\mathrm{Cu}}_{x}{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$, which superconducts below $\ensuremath{\sim}3\text{ }\text{ }\mathrm{K}$, predicted to possess superconducting state. We report point-contact spectra on cleaved...
We investigate the manifestation of stripes in in-plane resistivity anisotropy untwinned single crystals La2-xSrxCuO4 ( x = 0.02-0.04) and YBa(2)Cu(3)O(y) y 6.35-7.0). It is found that both systems show strongly temperature-dependent lightly hole-doped region grows with decreasing below approximately 6.60 despite orthorhombicity, which gives most direct evidence electrons self-organize into a macroscopically anisotropic state. The transport to be easier along direction spin already reported,...
The massless Dirac fermions residing on the surface of three-dimensional topological insulators are protected from backscattering and cannot be localized by disorder, but such protection can lifted in ultrathin films when three-dimensionality is lost. By measuring Shubnikov-de Haas oscillations a series high-quality Bi2Se3 thin films, we revealed systematic evolution conductance as function thickness found striking manifestation protection: metallic transport abruptly diminishes below...
We show that in the new topological-insulator compound Bi(1.5)Sb(0.5)Te(1.7)Se(1.3) one can achieve a surfaced-dominated transport where surface channel contributes up to 70% of total conductance. Furthermore, it was found this material properties sharply reflect time dependence chemical potential, presenting sign change Hall coefficient with time. demonstrate such an evolution makes us observe both Dirac holes and electrons on surface, which allows reconstruct band dispersion across point.
We report successful spin injection into the surface states of topological insulators by using a pumping technique. By measuring voltage that shows up across samples as result pumping, we demonstrate spin-electricity conversion effect takes place in bulk-insulating ${\mathrm{Bi}}_{1.5}{\mathrm{Sb}}_{0.5}{\mathrm{Te}}_{1.7}{\mathrm{Se}}_{1.3}$ and Sn-doped ${\mathrm{Bi}}_{2}{\mathrm{Te}}_{2}\mathrm{Se}$. In this process, injected spins are converted charge current along Hall direction due to...
The superconductivity recently found in the doped topological insulator Cu(x)Bi₂Se₃ offers a great opportunity to search for superconductor. We have successfully prepared single-crystal sample with large shielding fraction and measured specific-heat anomaly associated superconductivity. temperature dependence of specific heat suggests fully gapped, strong-coupling superconducting state, but BCS theory is not full agreement data, which hints at possible unconventional pairing Cu(x)Bi₂Se₃....
To optimize the bulk-insulating behavior in topological insulator materials having a tetradymite structure, we have synthesized and characterized single-crystal samples of ${\mathrm{Bi}}_{2\text{\ensuremath{-}}x}{\mathrm{Sb}}_{x}{\mathrm{Te}}_{3\text{\ensuremath{-}}y}{\mathrm{Se}}_{y}$ solid solution at various compositions. We elucidated that there are series intrinsic compositions where acceptors donors compensate each other present maximal behavior. At such compositions, resistivity can...
We propose that resistivity curvature mapping (RCM) based on the in-plane data is a useful way to objectively draw electronic phase diagrams of high-Tc cuprates, where various crossovers are important. In particular, pseudogap crossover line can be conveniently determined by RCM. show experimental obtained RCM for Bi2Sr2-zLazCuO6+delta, La2-xSrxCuO4, and YBa2Cu3Oy, demonstrate universal nature crossover. Intriguingly, near optimum doping depicted appears occur rather abruptly, suggesting...
The emergence and the evolution of metallic charge transport in La_{2-x}Sr_{x}CuO_{4} system from lightly- to optimally-doped samples (x = 0.01 - 0.17) are studied. We demonstrate that high-quality single crystals in-plane resistivity shows a behavior for ALL values x at moderate temperatures hole mobility 300 K changes only by factor 3 0.17, where its x-dependence is found be intriguingly similar inverse antiferromagnetic correlation length. discuss an incoherent-metal picture...
We have performed angle-resolved photoemission spectroscopy on TlBiSe₂, which is a member of the ternary chalcogenides theoretically proposed as candidates for new class three-dimensional topological insulators. found direct evidence nontrivial surface metallic state showing an "X"-shaped energy dispersion within bulk-band gap. The present result unambiguously establishes that TlBiSe₂ strong insulator with single Dirac cone at Brillouin-zone center. observed gap 0.35 eV largest among known...
Although the Hall coefficient R_H is an informative transport property of metals and semiconductors, its meaning in cuprate superconductors has been ambiguous because unusual characteristics. Here we show that a systematic study La_{2-x}Sr_{x}CuO_{4} single crystals over wide doping range establishes qualitative understanding peculiar evolution, which turns out to reflect two-component nature electronic structure caused by development Fermi surface recently uncovered photoemission experiments.
The existence of topological superconductors preserving time-reversal symmetry was recently predicted, and they are expected to provide a solid-state realization itinerant massless Majorana fermions route quantum computation. Their first concrete example, CuxBi2Se3, discovered last year, but the search for new materials has so far been hindered by lack guiding principle. Here, we report point-contact spectroscopy experiments showing that low-carrier-density superconductor Sn_{1-x}In_{x}Te is...
We observed pronounced angular-dependent magnetoresistance (MR) oscillations in a high-quality ${\text{Bi}}_{2}{\text{Se}}_{3}$ single crystal with the carrier density of $5\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }{\text{cm}}^{\ensuremath{-}3}$, which is topological insulator residual bulk carriers. show that can be well simulated by using parameters obtained from Shubnikov-de Haas oscillations, clarifies are essentially due to Fermi surface. By completely elucidating this result...
We have performed spin- and angle-resolved photoemission spectroscopy of Bi2Te3 present the first direct evidence for existence out-of-plane spin component on surface state a topological insulator. found that magnitude polarization hexagonally deformed Fermi (FS) reaches maximally 25% in-plane counterpart while such sizable does not exist in more circular FS TlBiSe2, indicating hexagonal deformation is responsible deviation from ideal helical texture. The observed much smaller than expected...
The mixed-chalcogenide compound TlBiSSe realizes a three-dimensional (3D) Dirac semimetal state. In clean, low-carrier-density single crystals of this material, we found Shubnikov--de Haas oscillations to signify its 3D nature. Moreover, observed very large linear magnetoresistance (MR) approaching 10 000% in 14 T at 1.8 K, which diminishes rapidly above 30 K. Our analysis the magnetotransport data points possibility that MR is fundamentally governed by Hall field; although such situation...
We detected the spin polarization due to charge flow in nondegenerate surface state of a three-dimensional topological insulator by means an all-electrical method. The current bulk-insulating Bi1.5Sb0.5Te1.7Se1.3 (BSTS) was injected/extracted through ferromagnetic electrode made Ni80Fe20, and unusual current-direction-dependent magnetoresistance gave evidence for appearance polarization, which leads spin-dependent resistance at BSTS/Ni80Fe20 interface. In contrast, our control experiment on...
We have performed systematic angle-resolved photoemission spectroscopy of the topological crystalline insulator (TCI) Pb${}_{1\ensuremath{-}x}$Sn${}_{x}$Te to elucidate evolution its electronic states across phase transition. As previously reported, band structure SnTe ($x=1.0$) measured on (001) surface possesses a pair Dirac-cone located symmetrically $\overline{X}$ point in (110) mirror plane. Upon approaching transition into trivial at ${x}_{c}\ensuremath{\approx}0.25$, we discovered...