Topological states in honeycomb arrays of implanted acceptors in semiconductors

Abstract

Abstract We study a neutral honeycomb array of acceptors in a Group IV semiconductor. Tight-binding exhibits a band gap from different hopping of angular momentum $\pm\frac32$ and $\pm\frac12$, forming a topological insulator (TI). The hopping is \textit{even} under separate reversal of spatial and spin motions, unlike spin-orbit coupling. The TI is robust to Coulomb interactions and realistic electronic structure calculations show it survives for a range of spacings and distortions commensurate with the silicon growth surface, but has an instability towards spin density wave formation at large separations.