A new paradigm for the quantum spin Hall effect at high temperatures

TL;DR

This paper proposes a theoretical framework for achieving high-temperature quantum spin Hall effects in monolayer-substrate heterostructures, enabling practical applications of topological quantum states.

Contribution

It introduces a new paradigm utilizing heavy group-V element monolayers on SiC substrates to realize large-gap QSHE at room temperature.

Findings

Bulk gaps of several hundreds of meV predicted.

Successful realization of Bi/SiC with an 800 meV gap.

Potential for scalable device applications.

Abstract

The quantum spin Hall effect (QSHE) has formed the seed for contemporary research on topological quantum states of matter. Since its discovery in HgTe/CdTe quantum wells and AlGaAs/GaAs heterostructures, all such systems have so far been suffering from extremely low operating temperatures, rendering any technological application out of reach. We formulate a theoretical paradigm to accomplish the high temperature QSHE in monolayer-substrate heterostructures. Specifically, we explicate our proposal for hexagonal compounds formed by monolayers of heavy group-V elements (As, Sb, Bi) on a SiC substrate. We show how orbital filtering due to substrate hybridization, a tailored multi-orbital density of states at low energies, and large spin-orbit coupling can conspire to yield QSH states with bulk gaps of several hundreds of meV. Combined with the successful realization of Bi/SiC (0001), with a measured bulk gap of 800 meV reported previously [Reis et al., 10.1126/science.aai8142 (2017)], our paradigm elevates the QSHE from an intricate quantum phenomenon at low temperatures to a scalable effect amenable to device design and engineering.