Shusaku Imajo

Low-temperature heat capacity of the organic superconductor λ-(BETS)2GaCl4 in a temperature range between 0.6 and 10 K was measured for a single crystal sample by relaxation calorimetry technique. The contribution of electronic heat capacity in the superconducting state shows T2 dependence at lower temperature that indicates the existence of quasi-particle excitations from the line-nodal gap structure of d-wave pairing. The recovery of the electronic heat capacity coefficient, γ by magnetic fiel

We investigate low-temperature electronic properties of the nondimeric organic superconductor β^{''}-(ET)_{4}[(H_{3}O)Ga(C_{2}O_{4})_{3}]PhNO_{2}. By examining ultrasonic properties, charge disproportionation (CD) without magnetic field dependence is detected below T_{CD}∼8 K just above the superconducting critical temperature T_{c}∼6 K. From quantum oscillations in high fields, we find variation in the Fermi surface and mass enhancement induced by the CD. Heat capacity studies elucidate that th

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 angle) anisotropic features in the superconducting electronic heat capacity Cele. The polar angle (θ) dependences of Cele have a simple twofold periodicity caused by the anisotropy of the critical field Hc2. In contrast, the azimuthal angle (ϕ) dependences show asymmetric anisotropi

We examine high-magnetic-field features of the superconducting state of the organic superconductor, κ-(BEDT-TTF)2Cu[N(CN)2]Br, with an emphasis on the emergence of the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state. In the H–T superconducting phase diagram in the parallel-field configuration, a significant upturn of the upper critical field with decreasing temperature was observed in the high-field region exceeding 30 T. We further indicate that the phase diagram can be universally discussed thro

Magnetic-field-angle-resolved heat capacity of dimer-Mott organic superconductors $\ensuremath{\kappa}\text{\ensuremath{-}}{(\mathrm{BEDT}\text{\ensuremath{-}}\mathrm{TTF})}_{2}X$ is reported (BEDT-TTF and $X$ represent bis(ethylenedithio)tetrathiafulvalene and a monovalent anion, respectively). Temperature and field dependence of heat capacity indicates that the superconductivity has line nodes on the Fermi surface, which is a typical feature of $d$-wave superconductivity. In-plane field-angle

Exotic superconductivity is formed by unconventional electron pairing and exhibits various unique properties that cannot be explained by the basic theory. The Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state is known as an exotic superconducting state in that the electron pairs have a finite center-of-mass momentum leading to a spatially modulated pattern of superconductivity. The spatial modulation endows the FFLO state with emergent anisotropy. However, the anisotropy has never been experimentall

In this work, the thermodynamic properties of the organic superconductor $\ensuremath{\lambda}\text{\ensuremath{-}}{(\mathrm{BETS})}_{2}{\mathrm{GaCl}}_{4}$ are investigated to study a high-field superconducting state known as the putative Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase. We observed a small thermodynamic anomaly in the field ${H}_{\mathrm{FFLO}}\phantom{\rule{4pt}{0ex}}\ensuremath{\sim}10$ T, which corresponds to the Pauli limiting field ${H}_{\mathrm{P}}$. This anomaly probably o

We have constructed a Doppler-shifter-type pulsed ultra-cold neutron (UCN) source at the Materials and Life Science Experiment Facility of the Japan Proton Accelerator Research Complex. Very cold neutrons (VCNs) with 136 m s[−1] velocity in a neutron beam supplied by a pulsed neutron source are decelerated by reflection on an m=10 wide-band multilayer mirror, yielding pulsed UCNs. The mirror is fixed to the tip of a 2000 rpm rotating arm moving with 68 m s[−1] velocity in the same direction as t

The authors experimentally investigate chemical pressure effects on electronic states of a series of \ensuremath{\beta}\ensuremath{''}-type organic conductors. Chemical substitutions in counter layers change the electronic states from metal to superconductivity coexisting with charge disproportionation because the size of counter-anions modify a lattice parameter, introducing chemical pressures to conducting layers. This work clarifies that electron correlations by the inter-site Coulomb repulsi

The condensation of paired fermions into superfluid states changes progressively depending on the coupling strength. At the midpoint of the crossover between Bardeen-Cooper-Schrieffer (BCS) weak-coupling and Bose-Einstein condensate (BEC) strong-coupling limits, paired fermions condensate most robustly, thereby leading to the emergence of a pseudogap due to enhanced pairing fluctuations. In the case of electrons in solids, excessively strong interactions often induce competing electronic orders

The superconducting phase diagram for a quasi-two-dimensional organic superconductor, κ-(BEDT-TTF)2Cu[N(CN)2]Br, was studied using pulsed magnetic field penetration depth measurements under rotating magnetic fields. At low temperatures, Hc2 was abruptly suppressed even by small tilts of the applied fields owing to the orbital pair-breaking effect. In magnetic fields parallel to the conducting plane, the temperature dependence of the upper critical field Hc2 exhibited an upturn and exceeded the P

We carried out a systematic measurement and data analysis of low-temperature heat capacities of three BEDT-TTF-based superconductive compounds with [Formula: see text]-type structure, where BEDT-TTF is bis(ethylenedithio)tetrathiafulvalene so as to compare the character of the quasi-particle excitations reflected in the electronic heat capacity. We used an original relaxation calorimetry cell with much reduced addenda heat capacity as compared with previous works. The three compounds, [Formula:

We investigate the continuous variation of electronic states from a Fermi liquid to a quantum spin liquid induced by chemical substitution in the organic dimer-Mott system of $\ensuremath{\kappa}\ensuremath{-}{[{(\text{BEDSe-}\mathrm{TTF})}_{x}{(\text{BEDT-}\mathrm{TTF})}_{1\ensuremath{-}x}]}_{2}\mathrm{Cu}[\mathrm{N}{(\mathrm{CN})}_{2}]\text{Br}$. Electrical transport measurements reveal that the mixing of BEDSe-TTF into the BEDT-TTF layers induces a quantum Mott transition around $x=0.10$. Alt

Metal–organic frameworks (MOFs) present a diverse chemical platform, leading to innovative breakthroughs in functional materials due to their controllable properties. In recent years, significant progress has been made in the realm of MOF magnets, with a primary emphasis on developing new molecule-based magnets for various applications. Nevertheless, the potential of MOFs as a platform for understanding quantum magnetism is still cultivating. Herein, based on detailed high-magnetic-field experim