First Principles Calculations of a Topological Invariant for Thin Magnetically-Doped SnTe

Harnessing quantum anomalous hall effect materials for applications often requires insulating properties in the bulk. In thin films, bulk conductivity can be affected by surface termination and strain induced by the substrate. Furthermore, interactions between the top and bottom surfaces may alter the band topology of the material and therefore the Chern number of the quantum anomalous hall state. To assess these effects, we performed density functional theory calculations of the electronic structure for SnTe thin films with differing thickness, strain, surface termination, and Cr-doping. We also calculated the Chern number for these cases. We found that certain surface terminations allow for the multiple gapped Dirac cones of SnTe to align, creating a common insulating gap. Furthermore, magnetism through Cr-doping is calculated to produce a non-zero Chern number.