Ambient-Pressure Organic Dirac Electron State in $\alpha$-(BETS)$_2$AuCl$_2$

TL;DR

This paper reports the discovery of an ambient-pressure Dirac electron state in a new organic conductor, characterized by unique transport properties and identified as a quasi-3D massive Dirac semimetal through first-principles calculations.

Contribution

It presents the first observation of an ambient-pressure Dirac electron state in $eta$-(BETS)$_2$AuCl$_2$, expanding the understanding of organic Dirac materials without high-pressure conditions.

Findings

Observation of large positive in-plane magnetoresistance.

Detection of anomalous negative interlayer magnetoresistance.

Identification of a quasi-3D massive Dirac semimetal state.

Abstract

We report an ambient-pressure Dirac electron (DE) state in a new organic conductor, $\alpha$-(BETS)$_2$AuCl$_2$ (BETS = bis(ethylenedithio)tetraselenafulvalene). This salt exhibits characteristic transport properties, including large positive in-plane and anomalous negative interlayer magnetoresistance. These signatures closely resemble the high-pressure DE states of $\alpha$-(ET)$_2$I$_3$ (ET = bis(ethylenedithio)tetrathiafulvalene). First-principles calculations including spin-orbit coupling identify the electronic state as a quasi-three-dimensional massive Dirac semimetal with residual Fermi pockets. This discovery provides a valuable platform for exploring bulk Dirac fermions without the complexity of high-pressure measurements.