Temperature-Induced Topological Phase Transitions: Promoted versus Suppressed Nontrivial Topology

Contrary to previous two-band model studies which find increasing temperature would induce a topological phase transition, we show here through first-principles calculations that the opposite is also realizable, depending on the material's full band structure and symmetry of the electron-phonon coupling potential. This finding explains recent experimental results by Wojek et al. [Nat. Commun. 6, 8463 (2015)]. We show that the topological phase diagram of BiTldS(1-delta)Sed(delta))(2) as a function of doping and temperature contains two distinct regions with nontrivial topology. In BiTlS2, the phonons promote the topological phase at high temperature, while in BiTlSe2, the system is driven back into the trivial phase.