A5029906861- Organic and Molecular Conductors Research
- High-pressure geophysics and materials
- Magnetism in coordination complexes
- Diamond and Carbon-based Materials Research
- Physics of Superconductivity and Magnetism
- Perovskite Materials and Applications
- Metal and Thin Film Mechanics
- N-Heterocyclic Carbenes in Organic and Inorganic Chemistry
- Iron-based superconductors research
- Solid-state spectroscopy and crystallography
- Molecular Junctions and Nanostructures
- Energetic Materials and Combustion
- Boron and Carbon Nanomaterials Research
- Geological and Geochemical Analysis
- Carbon Nanotubes in Composites
- nanoparticles nucleation surface interactions
- Magnetic and transport properties of perovskites and related materials
- Nuclear materials and radiation effects
- Crystal Structures and Properties
- Icing and De-icing Technologies
- Astro and Planetary Science
- Luminescence Properties of Advanced Materials
- Arctic and Antarctic ice dynamics
- Microwave Dielectric Ceramics Synthesis
- Silicon Nanostructures and Photoluminescence
Saitama University
2012-2025
RIKEN
2023
Hokkaido University
1976-2021
Ames National Laboratory
2020
Iowa State University
2020
National Institute for Materials Science
1999-2014
Hugoniot curve (shock velocity vs particle and pressure density) of $\ensuremath{\beta}\ensuremath{-}{\mathrm{Si}}_{3}{\mathrm{N}}_{4}$ has been measured up to 150 GPa by a two-stage light gas gun an inclined-mirror method. The elastic limit is detected be about 16 GPa. Above \ensuremath{\sim}36 GPa, phase transition from $c\ensuremath{-}{\mathrm{Si}}_{3}{\mathrm{N}}_{4}$ discovered. kinetics very sluggish. This does not seem complete at the highest achieved in this work, but extrapolation...
The Hugoniot compression curve for 6H polytype SiC has been determined to pressures of 160 GPa by a two-stage light-gas gun and an optical method which provides direct measurements shock velocity particle the compressed SiC. A phase transition detected at 105\ifmmode\pm\else\textpm\fi{}4 GPa, with volume reduction 15\ifmmode\pm\else\textpm\fi{}3 %. This change suggests that high-pressure sixfold coordination most probably rocksalt structure. behaviors diamond structure Si other polytypes...
We demonstrated X-ray structural analysis of the pressure-induced superconductor, $\beta'$-ET$_2$ICl$_2$ under extremely high-pressure conditions, where ET denotes bis(ethylenedithio)tetrathiafulvalene. This material has been known as highest transition temperature ($T_c$) superconductor among organic superconductors ($T_c=14.2$ K at $8.2$ GPa). On basis experimental results, ab-initio models were derived using constrained random phase approximation. revealed that Lifshitz exists behind Mott...
Hugoniot measurements on the highly dense, pure B4C polycrystal were performed by inclined-mirror method to study elastoplastic transition and search phase transition. In streak photographs, smoothly jagged structure was observed at free-surface shape in plastic region. The Hugoniot-elastic limit (HEL) has been determined be approximately 19.5GPa. region, a kink particle velocity of around 1.26km∕s. shock (US)–particle (UP) relations region given US=3.7+5.4UPkm∕s Up range 0.54–1.26km∕s...
Low-temperature heat capacity of the organic superconductor λ-(BETS)2GaCl4 in a temperature range between 0.6 and 10 K was measured for single crystal sample by relaxation calorimetry technique. The contribution electronic superconducting state shows T2 dependence at lower that indicates existence quasi-particle excitations from line-nodal gap structure d-wave pairing. recovery coefficient, γ magnetic field H1/2 is consistent with picture superconductor. In spite different packing typical...
We performed $^{13}\mathrm{C}$ NMR measurements on the unconventional organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ to clarify its electronic properties in paramagnetic state. found that spin-lattice relaxation rate divided by temperature $1/{T}_{1}T$ shows Curie-like enhancement above 55 K arises from an antiferromagnetic fluctuation. In addition, we additional of below 10 K, where Knight shift decreases and linewidth spectra is...
The phase transformation behavior of hexagonal germanium nitride, including both α- and β-Ge3N4, has been studied under shock wave compression. compressed quenched samples indicate from into a cubic spinel structure (γ-Ge3N4). This is completed with increasing pressure up to 40–46 GPa (temperature 1300–1500 K). lattice constant γ-Ge3N4 measured be 0.820 63±0.000 19 nm, the crystal density 6.581 g/cm3, by powder x-ray diffraction. stability also investigated It found that very stable, at...
The condensation of paired fermions into superfluid states changes progressively depending on the coupling strength. At midpoint crossover between Bardeen-Cooper-Schrieffer (BCS) weak-coupling and Bose-Einstein condensate (BEC) strong-coupling limits, most robustly, thereby leading to emergence a pseudogap due enhanced pairing fluctuations. In case electrons in solids, excessively strong interactions often induce competing electronic orders instead superconductivity, experimental...
Angle-resolved heat capacity (ARHC) measurements with multi-directional magnetic fields for an organic superconductor λ-(BETS)2GaCl4 are performed to investigate the out-of-plane (polar angle) and in-plane (azimuthal anisotropic features in superconducting electronic Cele. The polar angle (θ) dependences of Cele have a simple twofold periodicity caused by anisotropy critical field Hc2. In contrast, azimuthal (ϕ) show asymmetric anisotropies including fourfold-like terms originating from gap...
Many prismatic ice crystals have been observed to grooves which circle the prism faces at right angles c-axis. In both natural and artificial appear when crystal is evaporating disappear it growing. A possible ice-twinning structure proposed explain these observations, analogous zinc-blende rotation twins implying a diamond-structured layer interface.
The spin-liquid candidate $\kappa$-(ET)$_2$Cu$_2$(CN)$_3$ [ET: bis(ethylenedithio)tetrathiafulvalene] does not exhibit magnetic ordering down to a very low temperature, but shows mysterious anomaly at 6 K. origin of the so-called K is still under debate. We carried out nuclear quadrupole resonance (NQR) measurements on copper sites insulating layers, which are sensitive charge dynamics unlike conventional spin-1/2 (NMR). main finding this study that observation sharp peak behavior in...
The ground state of $\lambda$-(BEDT-TTF)$_2$GaCl$_4$, which has the same structure as organic superconductor $\lambda$-(BETS)$_2$GaCl$_4$, was investigated by magnetic susceptibility and $^{13}$C NMR measurements. temperature dependence revealed an antiferromagnetic (AF) correlation with $J/k_{\rm B} \simeq$ 98 K. spectrum splitting divergence $1/T_1$ were observed at approximately 13 K, is associated AF transition. We found that commensurate according to discrete peak splitting, suggesting...
We attempted to assign the spin structure of a layered organic antiferromagnet, $\ensuremath{\kappa}$-(d8-BEDT-${\mathrm{TTF})}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\mathrm{Br}$, which is key material located closest Mott boundary at ambient pressure among this family compounds, by investigating its macroscopic magnetization thoroughly, motivated recent successful assignment an isostructural material,...
We performed $^{13}\mathrm{C}$-NMR experiment and measured spin-lattice relaxation rate divided by temperature $1/{T}_{1}T$ near the superconducting (SC) transition ${T}_{c}$ in $\ensuremath{\kappa}$-(BEDT-TTF)${}_{2}$Cu[N(CN)${}_{2}$]Br ($\ensuremath{\kappa}$-Br salt), $\ensuremath{\kappa}$-(BEDT-TTF)${}_{2}$Cu(NCS)${}_{2}$ ($\ensuremath{\kappa}$-NCS salt). observed reduction of starting at higher than $\ensuremath{\kappa}$-Br salt. Microscopic observation quasiparticle density states...
We performed $^{13}\mathrm{C}$-NMR measurements on an organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ to investigate the superconducting (SC) gap symmetry, where BETS stands for bis(ethylenedithio)tetraselenafulvalene. As temperature approaches 0 K, Knight shift in SC state decreases; nuclear spin-lattice relaxation rate $1/{T}_{1}$ shows cubic dependence below transition ${T}_{c}$ without a coherence peak. These results can be...