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

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.