Bi/Ge(111) system*

Experimentally realizable chiral topological superconductors are actively pursued since they are expected to host Majorana quasiparticles. Here we develop an effective tight-binding description of Pb₃Bi/Ge(111), a candidate system for realizing chiral p-wave topological superconductor [Nat. Phys. 15, 796 (2019)]. The model is demonstrated to be able to capture the two central characters of the electronic bands found in first-principle calculations, namely, the giant Rashba spin-orbit coupling and type-II van Hove singularity. By introducing local superconducting pairing and perpendicular Zeeman field, we show the system can transform into a chiral topological superconducting phase with Chern number C=2. The nontrivial topology is further confirmed by edge state calculations and manifested as two pairs of chiral Majorana edge modes propagating along the same direction. We also discuss the experimental conditions for observing such a topological state by taking account of realistic material parameters, including the Landé g-factor, upper critical magnetic field, and real-space length scale of the Majorana edge modes. This study provides a guide for realizing and detecting Majorana quasiparticles in the Pb₃Bi/Ge(111) system.