Topological states in honeycomb arrays of implanted acceptors in semiconductors

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 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.