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) NCAOBW2041-172310. 1038/ncomms9463. We show that the topological phase diagram of BiTl (S₁-⏓Se⏓) 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.