First Principles Study of Structural, Elastic, Electronic and Optical Features of the Non-centrosymmetric Superconductors SrMGe3 (Where M= Ir, Pt, and Pd)

doi:10.34104/ijmms.020.016028

Abstract

BaNiSn3-type superconductors SrIrGe3, SrPdGe3, and SrPtGe3 have a critical temperature of 1.80 K, 1.49K and 1.0K respectively have been reported recently. Employing the first-principles method based on the density functional theory, we have examined the physical properties including structural, elastic, electronic, and optical phenomena of all these structures. For all the phases our optimized lattice parameters are well accord to the experimental lattice parameters. The positive elastic constants of these compounds revealed that these superconductors possess mechanical stability in nature. The values of Pugh’s ratio and Poisson’s ratio ensured the brittle manner of these compounds and anisotropic behavior is ensured by the values of anisotropy factor. The soft nature of all compounds is confirmed by the bulk modulus analysis. The values of Vickers's hardness indicate that the rigidity decreased in the order of SrIrGe3>SrPtGe3>SrPdGe3. The overlapping of the conduction band and valence band at Fermi level indicates the zero band gaps and metallic nature of SrIrGe3, SrPdGe3, and SrPtGe3. The chief contribution around the Fermi level arises from Ir-5d, Ge-4s, 4p states for SrIrGe3 and Ge-4s, 4p states for SrPdGe3 and Pt-5d, Ge-4s, 4p for SrPtGe3 compound. The study of DOS, Mulliken atomic populations, and charge density ensured the existence of complex bonding in SrIrGe3, SrPdGe3, and SrPtGe3 with ionic, covalent, and metallic characteristics. The analysis of the dielectric function also ensured the metallic behavior of all these compounds.

Highlights

The noncentrosymmetric superconductors have attracted much consideration having their unique superconducting properties caused by the Rashba-type antysymmetric spin-orbit coupling which leads to a mixing of the spin-singlet and spin-triplet states [1]
The investigation of different properties of SrMGe3 compounds have been carried out using Cambridge Serial Total Energy Package (CASTEP) code based on the density functional theory (DFT) [31, 32]
The Ge-4s24p2, Sr4s24p65s2 and Ir-5d76s2; Ge-4s24p2, Sr-4s24p65s2 and Pd-4d10; Ge-4s24p2, Sr-4s24p65s2 and Pt-5d96s1 are treated as the valance electrons in the case of SrIrGe3, SrPdGe3 and SrPtGe3 respectively for pseudo atomic calculations

Summary

INTRODUCTION

The noncentrosymmetric superconductors have attracted much consideration having their unique superconducting properties caused by the Rashba-type antysymmetric spin-orbit coupling which leads to a mixing of the spin-singlet and spin-triplet states [1]. CeIrGe3 [12], CeIrSi3 [13,14,15] CeCoGe3 [16, 17] and CeRhSi3 [18, 19] with BaNiSn3-type structure have been found to exhibit pressure induced superconductivity This finding is very interesting because along the c-axis their structure lacks inversion symmetry. The electronic properties of these BaNiSn3-type NCS can affect their superconducting properties caused by electron-phonon interactions In this family, pressure-inducted heavy-fermion SC has been detected in CeCoGe3 (Tc = 0.7 [28]), CeRhSi3 (Tc = 0.72 [29]), and CeCoGe3 (Tc = 0.7 CeIrGe3 (Tc = 1.6 K [30]). Are given and the summary of our study is given

THEORITICAL METHODS

RESULTS AND DISCUSSION

D Total Charge Bond Population Lengths

COCLUSION