Discovery of $${\hat{\boldsymbol{C}}}_2$$ C ̂ 2 rotation anomaly in topological crystalline insulator SrPb

Abstract

New class of topological crystalline insulators (TCI) have been proposed, but are yet to be experimentally evidenced. Here, the authors evidence two massless Dirac fermions protected by the combination of time-reversal symmetry T and Ĉ 2y on the (010) surface of SrPb, confirming the Ĉ 2 rotation anomaly in the new class of TCIs.