Theoretical investigation of superconductivity in the non-centrosymmetric SrPtGe3 and CaPtSi3 compounds

Abstract

First-principles calculations are made to investigate structural, elastic, electronic, vibrational and electron-phonon interaction properties of non-centrosymmetric superconductors SrPtGe3 and CaPtSi3. Electronic structure calculation results show that the density of states at the Fermi level for both compounds mainly comes from the p electrons of Ge (or Si), which considerably hybridise with Pt d states. The calculated Eliashberg spectral function with and without spin-orbit interaction reveals that while all phonon branches are involved in the process of scattering of electrons near the Fermi level, the average electron-phonon coupling parameter values of 0.47 for SrPtGe3 and 0.49 for CaPtSi3 indicate that these compounds are phonon-mediated BCS-type superconductors with a weak strength. By using a reasonable value of = 0.11 for the effective Coulomb repulsion parameter, the superconducting transition temperatures for SrPtGe3 and CaPtSi3 are found to be 1.3 K and 2.4 K, respectively, which compare very well with the corresponding experimental values of 1.0 K and 2.3 K.