A5014093944- Organic and Molecular Conductors Research
- Rare-earth and actinide compounds
- Magnetism in coordination complexes
- Iron-based superconductors research
- Physics of Superconductivity and Magnetism
- Advanced Condensed Matter Physics
- N-Heterocyclic Carbenes in Organic and Inorganic Chemistry
- Magnetic and transport properties of perovskites and related materials
- Quantum and electron transport phenomena
- Perovskite Materials and Applications
- Solid-state spectroscopy and crystallography
- Magnetic Properties of Alloys
- Inorganic Chemistry and Materials
- Topological Materials and Phenomena
- Molecular Junctions and Nanostructures
- Electronic and Structural Properties of Oxides
- Inorganic Fluorides and Related Compounds
- Superconductivity in MgB2 and Alloys
- Magnetic properties of thin films
- Graphene research and applications
- Advanced Chemical Physics Studies
- Multiferroics and related materials
- Intellectual Capital and Performance Analysis
- 2D Materials and Applications
- Corporate Taxation and Avoidance
National Institute for Materials Science
2016-2025
University of Tsukuba
2012-2022
Suzuki (Japan)
2010-2013
Tokyo Institute of Technology
2012
Institute for Materials Research, Tohoku University
2010-2012
The University of Tokyo
2010
Institute of Metal Research
1992-2007
Ewha Womans University
2006
Japan Science and Technology Agency
2006
Osaka Prefecture University
2006
Significance The BCS-BEC (Bardeen–Cooper–Schrieffer––Bose–Einstein-condensate) cross-over bridges the two important theories of bound particles in a unified picture with ratio attractive interaction to Fermi energy as tuning parameter. A key issue is understand intermediate regime, where new states matter may emerge. Here, we show that FeSe extremely small, resulting this system can be regarded an extraordinary “high-temperature” superconductor located at verge cross-over. Most importantly,...
We report the measurements of de Haas--van Alphen (dHvA) effect for field ranges below and above metamagnetic transition (${\mathit{H}}_{\mathit{m}}$) in ${\mathrm{CeRu}}_{2}$${\mathrm{Si}}_{2}$. The dHvA frequency branches effective masses ranging from 1.5${\mathit{m}}_{0}$ to 120${\mathit{m}}_{0}$ observed ${\mathit{H}}_{\mathit{m}}$ agree with predictions itinerant f electron model, whereas those can be explained well localized model. All frequencies change abruptly around...
We investigate by electrical transport the field-induced superconducting state (FISC) in organic conductor $\ensuremath{\lambda}\ensuremath{-}(\mathrm{BETS}{)}_{2}{\mathrm{FeCl}}_{4}$. Below 4 K, antiferromagnetic-insulator, metallic, and eventually ground states are observed with increasing in-plane magnetic field. The FISC survives between 18 41 T can be interpreted terms of Jaccarino-Peter effect, where external field compensates exchange aligned ${\mathrm{Fe}}^{3+}$ ions. further argue...
We report an extremely high upper critical field ${B}_{c2}$ in the noncentrosymmetric heavy fermion superconductor ${\mathrm{CeRhSi}}_{3}$ for a magnetic $B$ along tetragonal $c$ axis. ${B}_{c2}(T=0)$ possibly reaching 30 T is much higher than ${B}_{c2}(0)=7\text{ }\text{ }\mathrm{T}$ $B\ensuremath{\perp}c$ and greatly exceeds paramagnetic limiting field. The strong anisotropy of ${B}_{c2}(0)$ with $B\ensuremath{\parallel}c$ qualitatively explained by pair-breaking mechanism specific to...
We have observed Shubnikov-de Haas oscillations in FeSe. The Fermi surface deviates significantly from predictions of band-structure calculations and most likely consists one electron hole thin cylinder. carrier density is the order 0.01 carriers/ Fe, an order-of-magnitude smaller than predicted. Effective energies as small 3.6 meV are estimated. These findings call for elaborate theoretical investigations incorporating both electronic correlations orbital ordering.
We report the results of SQUID and torque magnetometry an organic spin-1/2 triangular-lattice κ-H(3)(Cat-EDT-TTF)(2). Despite antiferromagnetic exchange coupling at 80-100 K, we observed no sign order down to 50 mK owing spin frustration on triangular lattice. In addition, found nearly temperature-independent susceptibility below 3 K associated with Pauli paramagnetism. These observations suggest development gapless quantum liquid as ground state. On basis a comparative discussion, point out...
Recently, intriguing phenomena of superconductivity, type-II Weyl semimetal or quantum spin Hall states were discovered in metastable 1T'-type VIB-group transition metal dichalcogenides (TMDs). Here, we report that monoclinic phase WS2 was and synthesized our experiments. The intrinsic superconducting observed with a temperature Tc 8.8 K which is the highest among previously reported TMDs without any fine-tuning process. Intersteing, topological insulator state, defined by invariant Z2, also...
Recent developments in research into superconductivity organic materials are reviewed. In the epoch-defining quasi-one-dimensional TMTSF superconductors with T c ∼1 K, decreases monotonically increasing pressure, as do signatures of spin fluctuations normal state, providing good evidence for magnetically-mediated pairing. Upper critical fields exceed Zeeman-limiting field by several times, suggesting triplet pairing or a transition to an inhomogeneous superconducting state at high magnetic...
We report measurements of resistance and ac magnetic susceptibility on FeSe single crystals under high pressure up to 27.2 kbar. The structural phase transition is quickly suppressed with pressure, the associated anomaly not seen above $\sim$18 superconducting temperature evolves nonmonotonically showing a minimum at $\sim12$ find another 21.2 K 11.6 This most likely corresponds antiferromagnetic found in $μ$SR [M. Bendele \textit{et al.}, Phys. Rev. Lett. \textbf{104}, 087003 (2010)]....
Under special conditions, a superconducting state where the order parameter oscillates in real space, so-called FFLO state, is theoretically predicted to exist near upper critical field, as first proposed by Fulde and Ferrell, Larkin Ovchinnikov. We report systematic measurements of interlayer resistance high magnetic fields 45 T two-dimensional magnetic-field-induced organic superconductor $\ensuremath{\lambda}\mathrm{\text{\ensuremath{-}}}(\mathrm{BETS}{)}_{2}{\mathrm{FeCl}}_{4}$, BETS...
We report the ac magnetic susceptibility χ and resistivity ρ measurements of EuFe 2 As under high pressure P . By observing nearly 100% superconducting shielding zero at =28 kbar, we establish that -induced superconductivity occurs T c ∼30 K in shows an anomalous linear temperature dependence from room down to same indicates antiferromagnetic order Eu 2+ moments with N ∼20 persists phase. The upper critical field is also determined.
We report on a band structure calculation and de Haas–van Alphen measurements of KFe 2 As . Three cylindrical Fermi surfaces are found. Effective masses electrons range from 6 to 18 m e , being the free electron mass. Remarkable discrepancies between calculated observed surface areas large mass enhancement (\({\gtrsim}3\)) highlight importance electronic correlations in determining structures iron pnicitide superconductors.
We show that the Fermi surface (FS) in antiferromagnetic phase of ${\mathrm{BaFe}}_{2}{\mathrm{As}}_{2}$ is composed one hole and two electron pockets, all which are three dimensional closed, sharp contrast to FS observed by angle-resolved photoemission spectroscopy. Considerations on carrier compensation Sommerfeld coefficient rule out existence unobserved pockets significant sizes. A standard band structure calculation reasonably accounts for FS, despite overestimated ordered moment. The...
The gap structure of Sr$_2$RuO$_4$, which is a longstanding candidate for chiral p-wave superconductor, has been investigated from the perspective dependence its specific heat on magnetic field angles at temperatures as low 0.06 K ($\sim 0.04T_{\rm c}$). Except near $H_{\rm c2}$, fourfold specific-heat oscillation under an in-plane rotating unlikely to change sign down lowest temperature K. This feature qualitatively different nodal quasiparticle excitations quasi-two-dimensional...
We have used the magneto-oscillatory behavior of quasi-two-dimensional orbits in charge-transfer organic salt (BEDT-TTF${)}_{2}$KHg(SCN${)}_{4}$ to probe its underlying magnetic ground states, which arise from coexisting quasi-one-dimensional nature material. The complex oscillations results field dependence these states. Our allow comparison between several competing models attempted describe unusual properties this
We report resistivity measurements performed on KFe 2 As single crystals down to T = 0.3 K and in magnetic fields up 17.5 T. The in-plane vs curve has a convex shape ∼50 shows dependence below ∼45 K. ratio of the c -axis resistivities is ∼10 at room temperature ∼40 4.2 superconducting upper critical field B c2 ( ) been determined from data: b (0) 4.47 1.25 anisotropy parameter Γ= / increases with 6.8 . strong curvature indicates existence spin paramagnetic effects.
The magnetic field-induced changes in the conductivity of metals are subject intense interest, both for revealing new phenomena and as a valuable tool determining their Fermi surface. Here, we report hitherto unobserved magnetoresistive effect ultra-clean layered metals, namely negative longitudinal magnetoresistance that is capable overcoming very pronounced orbital one. This correlated with inter-layer coupling disappearing fields applied along so-called Yamaji angles where vanishes....
We performed low-frequency ac first- and second-harmonic resistance measurements dc $I-V$ on bulk FeSe crystals in a temperature range between 1.8 150 K magnetic field up to 14 T. observed considerable resistance, indicative of nonreciprocal charge transport, some samples. By examining correlation contact resistances signals, we concluded that the was not due genuine transport effect but caused by joule heating at current through thermoelectric effect. Our conclusion is consistent with...
We have performed an extensive dHvA effect study of CeRu 2 Si to gain more insight into the nature metamagnetic transition. The angular dependence frequencies confirms transition Fermi surfaces from those itinerant f electron below field ( H m ) localized above . and effective masses are measured for all observed with fields parallel [001]. A waveform analysis suggests that up down spin electrons similar in size, whereas significantly different. amplitudes oscillations their anomalous ,...
The high magnetic field electronic state of the quasi-two-dimensional organic superconductor,$\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}\mathrm{Fe}{\mathrm{Br}}_{4}$ was investigated by resistance measurements. At very low temperatures, magnetic-field-induced superconductivity (FISC) observed under parallel to conducting layers. obtained phase diagrams are well reproduced Fisher's theory based on Jaccarino-Peter compensation mechanism, where external and internal caused...
We present an experimental demonstration of a graphene-based double quantum dot system, which exhibits single-electron transport two lateral dots coupled in series. Low-temperature measurements revealed honeycomb charge stability diagrams with varied (from weak to strong) interdot tunnel-coupling regime, and we have extracted the relevant parameters associated system. These results are important for realization integrated circuits electronics.
We have completely determined the Fermi surface in KFe$_2$As$_2$ via de Haas-van Alphen (dHvA) measurements. Fundamental frequencies $ε$, $α$, $ζ$, and $β$ are observed KFe$_2$As$_2$. The first one is attributed to a hole cylinder near X point of Brillouin zone, while others cylinders at $Γ$ point. also observe magnetic breakdown between $α$ $ζ$ suggest plausible explanation for them. experimental show deviations from predicted by band structure calculations. Large effective masses up 19...