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.