Wannier Center Analysis on Possible Three-Dimensional Topological Phases in \alpha-Type Layered Organic Conductors

TL;DR

This paper uses Wannier charge centers to analyze potential 3D topological phases in layered organic conductors, identifying Dirac/Weyl semimetal states and weak topological insulators, and clarifying their transport properties.

Contribution

It provides a unified Wannier center framework to classify and understand the topological states in layered organic conductors, revealing the nature of Dirac/Weyl semimetals and topological insulators.

Findings

Type-I Dirac semimetal explains chiral transport phenomena.

Multilayered BETS I3 exhibits a weak topological insulator state.

Strong topological insulator state is unlikely in these materials.

Abstract

Topological features of possible three-dimensional (3D) states in \alpha-type layered organic conductors are investigated within a unified framework based on Wannier charge centers (WCCs), aiming to identify their actual topological states. Among the 3D Dirac/Weyl semimetal states of multilayered \alpha-(ET)2I3, the type-I Dirac semimetal state, induced by interlayer spin-orbit coupling (SOC), most effectively explains the observed chiral transport phenomena attributed to the chiral magnetic effect, which originates from the spiral structures of the WCC sheets. In multilayered \alpha-(BETS)2I3, a 3D weak topological insulator (TI) state consistently emerges, irrespective of the presence of interlayer SOC and/or inversion symmetry breaking. The strong TI state suggested by experimental observations appears unlikely to be realized.