Electron-phonon superconductivity in $A$Pt$_3$P compounds: from weak to strong coupling

摘要

We study the newly discovered Pt phosphides $A$Pt$_3$P ($A$=Sr, Ca, La) [ T.Takayama et al. Phys. Rev. Lett. 108, 237001 (2012)] using first-principlescalculations and Migdal-Eliashberg theory. Given the remarkable agreement withthe experiment, we exclude the charge-density wave scenario proposed byprevious first-principles calculations, and give conclusive answers concerningthe superconducting state in these materials. The pairing increases from La toCa and Sr due to changes in the electron-phonon matrix elements andlow-frequency phonons. Although we find that all three compounds are welldescribed by conventional s-wave superconductivity and spin-orbit coupling ofPt plays a marginal role, we show that it could be possible to tune thestructure from centrosymmetric to noncentrosymmetric opening new perspectivestowards the understanding of unconventional superconductivity.