Strain-induced partially flat band, helical snake states and interface superconductivity in topological
crystalline insulators
Evelyn M. Y. Tang,
Massachusetts Institute of Technology
Topological crystalline insulators in IV-VI compounds host novel topological surface states consisting of
multi-valley massless Dirac fermions at low energy. Here we show that strain generically acts as an effective
gauge field on these Dirac fermions and creates pseudo-Landau orbitals without breaking time-reversal symmetry. We
predict the realization of this phenomenon in IV-VI semiconductor heterostructures, due to a naturally occurring
misfit dislocation array at the interface that produces a periodically varying strain field. Remarkably, the
zero-energy Landau orbitals form a flat band in the vicinity of the Dirac point, and coexist with a network of
snake states at higher energy. We propose that the high density of states of this flat band gives rise to
interface superconductivity observed in IV-VI semiconductor multilayers at unusually high temperatures, with
non-BCS behavior.