Two-dimensional time-reversal-invariant topological superconductivity in a doped quantum spin Hall insulator

摘要

Time-reversal-invariant topological superconductors have a full paring gap inthe bulk and gapless Majorana states at the edge or on the surface. Here, wetheoretically propose topological superconductivity in a doped quantum spinHall insulator. We study the pairing symmetry of doped Sn$X$ film within atwo-orbital model, and show that it realizes a topological superconductor whenthe intraorbital attractive interaction is stronger than the interorbitalinteraction, which is generic for a doped quantum spin Hall insulator withstrong spin-orbit coupling. Edge channels are studied in a tight-binding modelnumerically. Finally, we discuss the possible topological superconductivity inSn$X$ film by comparing to $3d$ superconductivity in bulk Sn.