Ab initio study of the PbTaSe2 -related superconducting topological metals

Abstract

Recent reports have demonstrated the Z2 topological property of the superconductor PbTaSe2 (Tc∼3.8 K). PbTaSe2 simultaneously exhibits superconductivity and nontrivial Z2 topology without the need for doping or proximity effect. Scanning tunneling microscopy confirms that the topological surface states are gapped by superconductivity, indicating the likelihood of the chiral px+ipy pairing mechanism. Motivated by these exciting findings, we predict by means of the first-principles scheme that ABSe2 (A=Pb or Sn and B=Ta or Nb) is also a superconductor with nontrivial Z2 topology. Among these, SnNbSe2 shows the highest Tc∼7.0 K. Due to the fact that the required energy resolution to detect the Majorana bound states is of the order of Δ/F, the predicted higher Tc of ABSe2 may help mitigate some experimental challenges and provides a better platform for the exploration of the topological superconductivity.