Topological insulators double perovskites: A₂TePoO₆ (A = Ca, Sr, Ba)

Based on first-principle calculations and direct density functional theory calculations of surface bands, we predict a new class of three-dimensional (3D) Z₂ topological insulators (TIs) with larger bulk bandgaps up to 0.4 eV in double perovskite materials A₂TePoO₆ (A = Ca, Sr, and Ba). The larger nontrivial gaps are induced by the symmetry-protected band contact along with band inversion occurring in the absence of spin-orbit coupling (SOC) making the SOC more effective than conventional TIs. The proposed materials are chemically inert and more robust to surface perturbations due to its intrinsic protection layer. This study provides the double perovskite material as a rich platform to design new TI-based electronic devices.