A5091660633- Quantum, superfluid, helium dynamics
- Atomic and Subatomic Physics Research
- Physics of Superconductivity and Magnetism
- Cold Atom Physics and Bose-Einstein Condensates
- Methane Hydrates and Related Phenomena
- Spacecraft and Cryogenic Technologies
- Superconducting Materials and Applications
- Quantum and electron transport phenomena
- High-pressure geophysics and materials
- Mechanical and Optical Resonators
- Advanced Chemical Physics Studies
- Force Microscopy Techniques and Applications
- Advanced X-ray Imaging Techniques
- Nonlinear Dynamics and Pattern Formation
- Crystallography and Radiation Phenomena
- Heat Transfer and Boiling Studies
- Near-Field Optical Microscopy
- Nuclear Physics and Applications
- Spectroscopy and Quantum Chemical Studies
- Strong Light-Matter Interactions
- Computational Physics and Python Applications
- Photonic Crystals and Applications
- Organic and Molecular Conductors Research
- Inorganic Fluorides and Related Compounds
- Optical and Acousto-Optic Technologies
Keio University
2010-2022
The University of Tokyo
1989-2022
RIKEN Center for Emergent Matter Science
2018-2020
RIKEN
2018-2019
SPring-8
2016
National Institute for Basic Biology
1996
University of Bayreuth
1994
We have observed a dynamical transition in the Wigner solid on liquid $^{4}\mathrm{He}$. The ac Corbino conductivity ${\ensuremath{\sigma}}_{\mathrm{xx}}$ jumps abruptly at certain input voltage and shows hysteretic behavior. threshold ${V}_{\mathrm{th}}$ has dependences magnetic field $B$ perpendicular to surface, frequency $\ensuremath{\omega}$, electron density ${n}_{s}$, electric ${E}_{\ensuremath{\perp}}$ as...
We report the first quantitative study of size-dependent suprefluid transition in $^{4}\mathrm{He}$ films adsorbed on porous glasses with pore diameters d from 50 to 10 000 \AA{}. ${\mathit{T}}_{\mathit{c}}$ for submonolayer decreases as increases up d=2900 \AA{}, whereas full-pore liquid d. The dependence and dissipation at reveal that vortex-pair unbinding length scales smaller than sizes determines superfluid transition. obtain diameter vortex core...
We have developed an experimental apparatus named KOTOBUKI-1 for use in coherent X-ray diffraction imaging experiments of frozen-hydrated non-crystalline particles at cryogenic temperature. For specimen stage with small positional fluctuation a long exposure time more than several minutes, we here pot cooled by the evaporation cooling effect liquid nitrogen. In addition, loading device is to bring specimens stored nitrogen vacuum. The allows data collection 66 K less 0.4 μm and provides...
We explore the superfluidity of 4He confined in a porous glass, which has nanopores 2.5 nm diameter, at pressures up to 5 MPa. With increasing pressure, is drastically suppressed, and superfluid transition temperature approaches 0 K some critical Pc approximately 3.4 The feature suggests that extreme confinement into induces quantum phase from nonsuperfluid Pc.
Coherent X-ray diffraction imaging (CXDI) is a technique for structure analyses of non-crystalline particles with dimensions ranging from micrometer to sub-micrometer. We have developed apparatus named TAKASAGO-6 use in single-shot CXDI experiments frozen-hydrated biological at cryogenic temperature free electron laser pulses provided repetition rate 30 Hz the SPring-8 Angstrom Compact free-electron LAser. Specimen are flash-cooled after being dispersed on thin membranes supported by...
We report the measurements of heat capacity $^{4}\mathrm{He}$ confined in nanoporous Gelsil glass that has nanopores 2.5-nm diameter at pressures up to 5.3 MPa. The a broad peak temperature much higher than superfluid transition obtained using torsional oscillator technique. provides definite thermodynamic evidence for formation localized Bose-Einstein condensates on nanometer length scales. dependence is described well by excitations phonons and rotons, supporting existence condensates.
We studied physiological roles of the yeast vacuole in phosphate metabolism using 31P-in vivo nuclear magnetic resonance (NMR) spectroscopy. Under starvation wild-type cells continued to grow for two three generations, implying that contain large pool sustain growth. During first four hours under starved condition, cytosolic level was maintained almost constant, while vacuolar decreased significantly. 31P-NMR spectroscopy on intact and perchloric acid (PCA) extracts showed drastic decrease...
We report measurements of noncontact friction between surfaces NbSe2 and SrTiO3 a sharp Pt-Ir tip that is oscillated laterally by quartz tuning fork cantilever. At 4.2 K, the coefficients on both metallic insulating materials show giant maximum at tip-surface distance several nanometers. The strongly correlated with an increase in spring constant These features can be understood phenomenologically distance-dependent relaxation mechanism distributed time scales.
Abstract We report a systematic experimental study of the anomalous nonlinear magnetotransport in Wigner solid (WS) trapped on liquid 4 He surface. The ac Corbino conductivity σ xx exhibits an abrupt jump at certain driving voltage. threshold input voltage V th for varies as ∝ B −0.8 ω −1 n 1.5 s E ⊥ , where B, ω, and are magnetic field, frequency, electron density pressing electric respectively. interpret transition between WS accompanied with periodic 4He surface deformation which...
Measurements of the dc resistivity surface-state electrons on liquid helium exposed to microwave radiation are reported. It is shown that resonant excitation accompanied by a strong increase in their resistivity, which opposite result expected from previously used two-level model. We show even very small fraction excited first state and decaying back due vapor-atom scattering strongly heat electron system, causing population higher subbands. The calculated change good agreement with observed data.
We report the measurement of electrical transport two-dimensional Wigner solid (WS) formed on free surface superfluid ${}^{3}\mathrm{He}\ensuremath{-}B$ down to $230\ensuremath{\mu}\mathrm{K}$. The resistance $R(T)$ dramatically decreases as temperature $T$ decreases, obeying Arrhenius' law, $R(T)\ensuremath{\propto}\mathrm{exp}[[\left(\ensuremath{-}\ensuremath{\Delta}(T){/k}_{B}T\right)$, with $\ensuremath{\Delta}(T)$ which we assign energy gap. That is, scattering ${}^{3}\mathrm{He}$...
We have studied the liquid - solid (L-S) phase transition of ^4He confined in nanoporous glass, which has interconnected nanopores 2.5 nm diameter. The L-S boundary is determined by measurements pressure and thermal response during slow cooling warming. Below 1 K, freezing elevated to 1.2 MPa from bulk pressure, appears be independent temperature. T-independent implies existence a localized Bose-Einstein condensation state, long-range superfluid coherence destroyed narrowness random potential.
4 He confined in nanoporous media is an excellent model boson system a confinement potential. We have studied the superfluid and thermodynamic properties of porous glass that has nanopores 2.5 nm diameter. It shown produces new quantum state, localized Bose–Einstein condensation (LBEC) markedly alters pressure–temperature ( P – T ) phase diagram. In LBEC state global coherence destroyed by strong atomic correlation or random potential substrate. The formation leads to anomalous reduction...
We present new low temperature magnetoconductivity $({\ensuremath{\sigma}}_{\mathrm{xx}})$ measurements for the two-dimensional electron system on a liquid helium surface and theoretical concept of inelastic quantum magnetotransport that explains data. It is shown predictions ${\ensuremath{\sigma}}_{\mathrm{xx}}$ made in elastic approximation are valid only within limited range which narrows with magnetic field increase. The dependencies observed can be perfectly described as interplay...
The origin of supersolidity solid 4He, which was reported by Kim and Chan, has not yet been clarified. Although Bose-Einstein condensation zero-point vacancies (ZPVs) initially considered to be a possible origin, recent studies imply that crystal imperfections in the samples are strongly associated with observed supersolid behaviors. In two-dimensional (2D) 3He system on graphite, other hand, novel phase due quantum hopping ZPVs found. This suggests form also 2D 4He systems their results...
We have investigated the intersubband transitions of surface-state electrons (SSE) on liquid 3 He induced by microwave radiation at temperatures from 1.1 K down to 0.01 K. Above 0.4 K, transition linewidth is proportional density vapor atoms. This proportionality explained well Ando's theory, in which determined electron–vapor atom scattering. However, larger than calculated result a factor 2.1. discrepancy strongly indicates that theory underestimates scattering rate. At lower temperatures,...
A frequency modulation-atomic force microscope (FM-AFM) designed to measure atomic scale topography at low temperatures is developed. Piezoelectric quartz tuning forks are employed as a sensor for use. In order perform high-resolution measurements, detection of attractive forces between tip and sample important. Measurements van der Waals on SrTiO3 substrate successfully performed down 4.2 K by minimizing an amplitude the fork. Topographic imaging steps also achieved room in vacuum (10-3 Pa).
We have examined superfluid properties of He4 confined to a nanoporous Gelsil glass that has nanopores 2.5nm in diameter. The pressure-temperature phase diagram was determined by torsional oscillator, heat capacity, and pressure studies. transition temperature Tc approaches zero at 3.4MPa, indicating novel quantum transition. By capacity measurements, the nonsuperfluid adjacent solid phases is identified be nanometer-scale, localized Bose condensation state, which global coherence destroyed....
We have constructed a versatile current to voltage (I-V) converter operating at liquid helium temperature, using commercially available all-CMOS OPamp. It is valuable for cryogenic measurements of electrical nano-pico amperes, example, in scanning probe microscopy. The I-V thermally linked bath and self-heated up 10.7 K. confirmed its capability transimpedance gain 106 V/A bandwidth from DC 200 kHz. In order test the practical use frequency-modulation atomic force microscope, we measured...
Helium films show various quantum phases that undergo phase transitions by changing coverage n. We found anomalous elastic phenomena in bosonic 4He and fermionic 3He adsorbed on a glass substrate. The stiffen under AC strain at low temperature with an excess dissipation. onset of the stiffening decreases to 0 K as n approaches critical nc. anomaly is explained thermal activation helium atoms from localized extended states distributed energy gap. determine for first time band structure...
We present measurements and a theoretical concept of the nonlinear transport in two-dimensional Wigner solid on free surface normal superfluid $^{3}\mathrm{H}\mathrm{e}$. have observed transition from Ohmic to over wide temperature range, $200\text{ }\ensuremath{\mu}\mathrm{K}$ }\mathrm{m}\mathrm{K}$ at low electron velocities. The field-velocity ($E\mathrm{\text{\ensuremath{-}}}v$) characteristics show nonmonotonic structure with particular local maxima. attribute this nonlinearity...