Interfacial-state coupling induced topological phase transitions in materials with multiple valleys

A defining feature of topological insulating phases is symmetry-protected interfacial Dirac states. By exploiting couplings of multiple interfacial Dirac valleys in a binary superlattice, we establish that contrasting valley parity exchange forges a unifying bridge to create various topological phases. Ab initio simulations demonstrate that topological phase transitions can occur due to valley-dependent interfacial-state coupling in both two-dimensional and three-dimensional IV-VI topological crystalline insulators with multiple valleys.