A complementary screening for quantum spin Hall insulators in 2D exfoliable materials

Abstract

Quantum spin Hall insulators are a class of topological materials that has been extensively studied during the past decade. One of their distinctive features is the presence of a finite band gap in the bulk and gapless, topologically protected edge states that are spin-momentum locked. These materials are characterized by a $\mathbb{Z}_2$ topological order where, in the 2D case, a single topological invariant can be even or odd for a trivial or a topological material, respectively. Thanks to their interesting properties, such as the realization of dissipationless spin currents, spin pumping and spin filtering, they are of great interest in the field of electronics, spintronics and quantum computing. In this work we perform an high-throughput screening of Quantum spin Hall insulators starting from a set of 783 2D exfoliable materials, recently identified from a systematic screening of the ICSD, COD, and MPDS databases. We find a new $\mathbb{Z}_2$ topological insulator (HgNS) as well as 3 already known ones and 7 direect gap metals that have the potential of becoming Quantum spin Hall insulators under a reasonably weak external perturbation.