arXiv subjects

Mitsuyuki Sato

Publications and source records attributed to Mitsuyuki Sato.

5 recordsLinked to original sources

arXiv2025

Helical Edge Transport in the ν= 0 Quantum Hall Ferromagnetic State of an Organic Dirac Fermion System

We experimentally confirm the ν= 0 quantum Hall ferromagnetic (QHF) state, accompanied by helical edge states, in the layered organic Dirac-fermion system α-(ET)2I3 by demonstrating helical edge transport in multilayers. The saturation of interlayer magnetoresistance (MR) in the high-magnetic-field quantum limit does not scale with the sample cross-sectional area and appears when the magnetic field is oriented along the side surface. The in-plane MR exhibits a similar angle dependence, whereas this feature disappears in the Corbino geometry where no edge channels are present. These results are consistent with helical edge transport in the multilayer QHF state. They also rule out the possibility that the observed angle-dependent MR arises from the chiral magnetic effect expected for a 3D Dirac or Weyl semimetal.

cond-mat.mes-hall↗

arXiv2023

Quantized thermoelectric Hall plateau in the quantum limit of graphite as a nodal line semimetal

We performed thermoelectric Hall conductivity $α_{xy}$ measurements on single-crystal graphite in the quantum limit up to 13 T. Both electrical and thermoelectric transport measurements were performed on the same crystal to extract pure $α_{xy}$, avoiding any sample quality dependence. The $α_{xy}$ converges to a plateau in the quantum limit with a linear dependence on temperature. This behavior is analogous to the quantized thermoelectric Hall effect (QTHE) observed in three-dimensional Dirac/Weyl nodal-point semimetals, and experimentally confirms a theoretical proposal on the QTHE in semimetals with nodal lines as in graphite.

cond-mat.mes-hall↗

arXiv2021

Experimental Confirmation of Massive Dirac Fermions in Weak Charge-Ordering State in α-(BEDT-TTF)_2I_3

The electronic structure of weak charge-ordering (CO) state just below the critical pressure in an organic conductor α-(BEDT-TTF)_2I_3 was experimentally investigated using peak structure in the temperature dependence of interlayer magnetoresistance (MR). Based on a minimal model considering multiple Landau levels (LLs), we discuss herein the MR peak as characteristic to multilayer massless/massive Dirac fermion (DF) systems. MR measured in the weak CO state exhibited a clear MR peak, and its magnetic-field dependence was consistent with the LL behavior of a massive DF with a small gap. Results indicate that the weak CO state in α-(BEDT-TTF)_2I_3 is a massive DF state.

cond-mat.str-el↗

arXiv2019

Experimental Confirmation of Quantum Hall Ferromagnetic State in an Organic Dirac Fermion System

We have experimentally confirmed the quantum Hall ferromagnetic state with Chern number ν=0, characterized by the helical edge state, in a layered organic Dirac fermion system α-(BEDT-TTF)_2I_3. The interlayer resistance saturates at low temperatures and high magnetic fields. It does not scale with the sample cross-sectional area in the saturating region, and resonantly depends on the magnetic field direction. These results strongly suggest that the helical edge state dominates transport. This is the first observation of the topological phase in organic molecular crystals.

cond-mat.str-el↗

arXiv2018

Anisotropy of Dirac cones and van Hove singularity in an organic Dirac fermion system

We propose an experimental method to examine the in-plane anisotropy of electronic structure in layered conductors. In the method, we measure the interlayer magnetoresistance as a function of in-plane magnetic field orientation. We applied it to an organic Dirac fermion system a-(BEDT-TTF)2I3 to experimentally determine the orientation of the anisotropic Dirac cones. It is concluded that the long axis of the elliptic constant-energy contours of the Dirac cone is tilted by approximately -30 deg from the crystalline a-axis to b-axis under hydrostatic pressures. Additionally, we observed a signature of van Hove singularity (which is a saddle point of the band dispersion) at 30-40 K above or below the Dirac point. The ridgeline of the saddle point is estimated as almost parallel to the crystalline b-axis.

cond-mat.str-el↗