Physical properties of hexagonal BaPtAs with noncentrosymmetric SrPtSb-type and centrosymmetric YPtAs-type crystal structures: Effects of spin-orbit coupling

Abstract

Recently, superconductivity in BaPtAs with the noncentrosymmetric SrPtSb and the centrosymmetric YPtAs-structure has been discovered. Its noncentrosymmetric and centrosymmetric structures make BaPtAs a charming compound for searching the effect of spin-orbit coupling (SOC) onto superconductors with broken and preserved spatial inversion symmetry. We have investigated the effect of SOC on the physical and electron-phonon interaction properties of these phases of BaPtAs by using the generalized gradient approximation of the density functional theory and the plane-wave pseudopotential method. The inclusion of SOC has moderate effect on the elastic and electronic properties, and on phonon frequencies for both phases of BaPtAs. However, SOC makes an opposite impact on their Eliashberg spectral function. For the noncentrosymmetric phase, this coupling decreases the strength of dominant peaks of Eliashberg spectral function, reducing the values of average electron-phonon coupling and superconducting transition temperature. The scenario is exactly opposite for the centrosymmetric phase. For both phases, the hybridized Pt-As vibrations play a strongly significant role in determining their electron-phonon interaction properties since their electronic states have the dominant contribution near the Fermi level. The superconducting temperature is estimated to be 2.87 K for the SrPtSb phase and 2.38 K for the YPtAs phase. These values compare well with the reported measured values of 2.8 K and 2.1--3.0 K, respectively.