Giant gap 3D topological insulator in double perovskites: A2BiAtO6 (A=Ca, Sr, Ba)

Abstract We predict new class of three-dimensional (3D) Z2 topological insulators (TIs) in A2BiAtO6 (A=Ba, Ca and Sr) double perovskites with band gaps due to spin-orbital couplings (SOC). By employing first-principle calculations based on the density functional theory (DFT), we obtain energy gaps of 0.70 , 0.71 and 0.72 eV for A2BiAtO6 with A=Ba, Ca and Sr, respectively. These energy band gaps are among the largest ever found so far and allow for potential room-temperature applications of their topological properties. The proposed materials are not only chemically more inert but also more robust against surface perturbations due to its intrinsic protection layer.