Three-Dimensional Topological Semimetal/Insulator States in \alpha-Type Organic Conductors with Interlayer Spin-Orbit Interaction

TL;DR

This paper investigates the electronic states of layered organic conductors, revealing conditions under which they exhibit topological semimetal or insulator phases influenced by interlayer spin-orbit interactions.

Contribution

It introduces a tight-binding model for -type organic conductors incorporating interlayer spin-orbit coupling, predicting topological phases consistent with experimental observations.

Findings

Realization of Dirac semimetal state in -(ET)2I3 due to interlayer spin-orbit coupling.

Weyl semimetal state emerges when inversion symmetry is broken in interlayer hoppings.

Topological insulator phase in -(BETS)2I3 is unlikely with inversion symmetry.

Abstract

We have studied the tight-binding model for the \alpha-type layered organic conductors, \alpha-(ET)2I3 and \alpha-(BETS)2I3, with a uniform interlayer coupling accompanied by spin-orbit interaction originating from the I3- anion potential. The model preserves the time reversal and inversion symmetries. In \alpha-(ET)2I3, the interlayer spin-orbit coupling realizes the experimentally suggested Dirac semimetal state with inversion symmetry. In contrast, the inversion breaking in interlayer hoppings realizes the Weyl semimetal state without spin-orbit coupling. In \alpha-(BETS)2I3, the proposed strong topological insulator is hardly realized with inversion symmetry.