Towards Material realizations of 2D Topological Superconductivities in Pb_1-xBi_x Systems

New material realization of two-dimensional (2D) topological superconductors (TSCs) can provide new platforms for experimentally detecting and manipulating Majorana quasiparticles, which in pairs serve as an exotic entity for nonlocal encoding of quantum information [1]. In this talk, I will focus possibilities of realizing 2D intrinsic topological superconductivity in a new material family, namely atomic-layer-thin Pb_1-xBi_x alloys. Based on first-principles calculations, three nearly energetically degenerate structural configurations of the prototypical system Pb₃Bi grown on a Ge substrate are identified and labeled respectively as T₁, H₃ and T₄ [2]. All three structures possess large Rashba energy band splittings and van Hove singularities (VHS) in the density of states. With proper tensile strains, H₃ and T₄ configurations are demonstrated to have nontrivial band topology characterized by topological edge states. To investigate the superconductivity, an effective formalism that respects hexagonal symmetry, Rashba splitting, VHS and electron-electron interactions is developed with parameters obtained from first-principles calculations. Our renormalization group analysis shows that a chiral p-wave superconducting phase dominates over other competing orders. Given these results, we identify hole-doped Pb₃Bi/Ge(111) as an appealing platform for realizing intrinsic 2D topological superconductivity [3].