Electron and Phonon Band-Structure Calculations for the Antipolar SrPt3P Antiperovskite Superconductor: Evidence of Low-Energy Two-Dimensional Phonons

Abstract

SrPt3P has recently been reported to exhibit superconductivity with T-c = 8.4 K. To explore its superconducting mechanism, we have performed electron and phonon band calculations based on the density functional theory, and found that the superconductivity in SrPt3P is described well by the strong coupling phonon-mediated mechanism. We have demonstrated that superconducting charge carriers come from pd pi-hybridized bands between Pt and P ions, which couple to low energy (similar to 5 meV) phonon modes confined on the ab in-plane. These in-plane phonon modes, which do not break antipolar nature of SrPt3P, enhance both the electron-phonon coupling constant lambda and the critical temperature T-c. There is no hint of a specific phonon softening feature in the phonon dispersion, and the effect of the spin-orbit coupling on the superconductivity is found to be negligible.