The role of strontium deficiency and pressure on electron-phonon superconductivity in Sr3SnO

Abstract

This paper presents detail and systematic study of the role of strontium deficiency and pressure effect on electron-phonon superconductivity in Sr3SnO (SSO) using the combined density functional theory (DFT) and density functional perturbation theory (DFPT). The high logarithmic averaged phonon frequency (ωln = 709.49 K) and weak electron-phonon coupling (λ = 0.272) in Sr2.5SnO produce a maximum Tc of 4.56 K, which fairly agrees with the experimental value of ∼5 K. The breaking of SrO bonds causes charge transfer from Sn to Sr. We observed pressure induced phonon softening in stoichiometric SSO and superconductivity from 80 GPa. The charge transfer by applied pressure is responsible for the soft behavior of certain acoustic phonons. We predict that electron-phonon coupling is sufficient to understand the superconductivity mechanism in stoichiometric SSO under high pressure and Sr-deficient SSO.