Stacking disorder in Topological Insulators and Dirac/Weyl (semi)metals

The recent vast developments of newly discovered and revisited spin-orbit coupled materials are largely fueled by their potential as topological insulators or (semi)metals. These topological states were first understood using band theories, where lattice momenta are conserved. Subsequently, there were also theoretical studies on disordered topological states. However, applications to materials has been relatively limited. We theoretically investigate the phase-change material family (GeTe)_m(Sb₂Te₃)_n, which is known to undergo temperature/disorder-driven amorphous-crystalline as well as metal-insulator phase transitions. More recently, under certain distinct crystalline stacking layer configurations, the materials were proposed to be topological insulating and Dirac/Weyl (semi)metallic. Using an effective electronic model, we study the effects of stacking disorder on the topological phase transitions.