arXiv subjects

T. Tsumuraya

Publications and source records attributed to T. Tsumuraya.

4 recordsLinked to original sources

arXiv2023

Role of hydrogen bonding in charge-ordered organic conductor $α$-(BEDT-TTF)$_2$I$_3$ probed by $^{127}$I nuclear quadrupole resonance

We present $^{127}$I nuclear quadrupole resonance spectra and nuclear relaxation of $α$-(BEDT-TTF)$_2$I$_3$ that undergoes a charge-ordering transition. Only one of the two I$_3$ anion sites shows a significant differentiation in the electric field gradients across the first-order transition. The charge modulation only in the BEDT-TTF layers can not reproduce; instead, an anion-donor interaction accompanied by hydrogen bonding is necessary. The dominating source for the nuclear relaxation is the local libration of the I$_3$ anions, but an anomalous peak is detected just below the transition, as observed by $^{13}$C NMR.

cond-mat.str-el↗

arXiv2022

A Monomer Mott Insulator (BEDT-TTF)Cu[N(CN)$_2$]$_2$ as a Potential Nodal Line System

We report the band structure calculations and the experimental results of resistivity and magnetic susceptibility in a spin-1/2 (BEDT-TTF)$^{\bullet +}$ monomer Mott insulator (BEDT-TTF)Cu[N(CN)$_2$]$_2$. The band calculations indicate a Dirac semimetal state with nodal lines at the Fermi level. The resistivity and the magnetic susceptibility as functions of temperature are well interpreted in terms of the monomer Mott insulating state instead of the expected semimetal state probably owing to strong electron correlation. In addition, we find that an Arrhenius-type steep reduction of the paramagnetic susceptibility appears below approximately 25 K, which indicates a spin-singlet ground state.

cond-mat.str-el↗

arXiv2021

Large Diamagnetism and Electromagnetic Duality in Two-dimensional Dirac Electron System

A Dirac electron system in solids mimics a relativistic quantum physics that is compatible with Maxwell's equations, by which we anticipate unified electromagnetic responses. We find a large orbital diamagnetism only along the interplane direction and the nearly temperature-independent conductance of the order of e2/h for the new 2D Dirac organic conductor, a-(BETS)2I3. Distinct from conventional electrons in solids whose nonrelativistic effects bifurcate electric and magnetic responses, the observed orbital diamagnetism scales the electrical conductivity for a wide temperature range. This demonstrates that an electromagnetic duality that is valid only within the relativistic framework is revived in solids.

cond-mat.mes-hall↗

arXiv2013

An ARPES Study of the Electronic Structure of the Quantum Spin Liquid EtMe3Sb[Pd(dmit)2]2

The electronic structure of a quantum spin liquid compound, EtMe3Sb[Pd(dmit)2]2, has been studied with angle-resolved photoemission spectroscopy, together with two other Pd(dmit)2 salts in the valence bond solid or antiferromagnetic state. We have resolved several bands that have negligible dispersions and fit well to the calculated energy levels of an isolated [Pd(dmit)2]2 dimer. EtMe3Sb[Pd(dmit)2]2 being a Mott insulator, its lower Hubbard band is identified, and there is a small gap of ~ 50 meV between this band and the chemical potential. Moreover, the spectral features exhibit polaronic behavior with anomalously broad linewidth. Compared with existing theories, our results suggest that strong electron-boson interactions, together with smaller hopping and on-site Coulomb interaction terms have to be considered for a realistic modeling of the organic quantum spin liquid systems like the Pd(dmit)2 salt.

cond-mat.str-el↗