Microscopic characterization of the superconducting gap function in Sn 1 -x In x Te

Superconductivity in the doped topological crystalline insulator Sn1-xInx Te is studied by first-principles calculation based on superconducting density functional theory (SCDFT) and tunneling spectroscopy. By considering the spin-orbit coupling and frequency dependence of the screened Coulomb interaction in SCDFT, we succeed in reproducing the critical temperature of Sn(1-x)In(x )quantitatively, in which the spin-orbit coupling is found to play an essential role. The leading gap function is a conventional s wave with moderate anisotropy in k space, and we find that the subdominant odd-parity instability is significantly weaker than the s-wave instability. We perform tunneling spectroscopy measurement and confirm that the spectrum is consistent with the calculated gap function.