SrAuSi₃: A Noncentrosymmetric Superconductor

Abstract

A novel strontium−gold silicide (SrAuSi 3 ) was successfully synthesized for the first time using a high-pressure technique, at ∼6 GPa. X-ray Rietveld analysis and scanning transmission electron microscopy studies clearly revealed that SrAuSi 3 crystallizes in a BaNiSn 3 -type structure, in space group I4mm with the following lattice parameters: a = 4.4090(1) Å, and c = 9.9475(3) Å. The structure was found not to have inversion symmetry in real space. From direct measurements of polycrystalline SrAuSi 3 , the electrical resistivity was zero, the static magnetic susceptibility was almost a full volume Meissner diamagnetic signal, and the specific heat exhibited a sharp jump, all of which were accompanied by a phase transition due to bulk superconductivity at a critical temperature (T C ) of 1.54 K. The SrAuSi 3 compound is the first noncentrosymmetric superconductor that includes Au as a principal constituent element.

Theoretical investigation of superconductivity in SrAuSi3 and SrAu2Si2

“…The spin-orbit interaction is included as a perturbation to the scalar-relativistic equations. This theoretical work [24] reveals that the spin-orbit interaction for this superconductor has only negligible effect on the band structure around the Fermi energy. Moreover, this theoretical work [24] shows that the band structure around the Fermi energy is dominated by Si p states and the mechanism of superconductivity is suggested as phonon induced.…”

“…Recently, the lattice parameters, electronic structures, elastic constants, Vicker's hardness and thermodynamics properties of SrAuSi 3 were systematically investigated by using first-principles and the quasi-harmonic Debye model [35]. In this theoretical work [35], the superconducting transition temperature (T c ) for SrAuSi 3 is calculated to be 9.94 K which is much larger than its experimental value of 1.54 K [24].…”

“…A recent experiment shows that SrAuSi 3 [24], which also has the body-centered tetragonal BaNiSn 3 -type structure, exhibits superconductivity with a critical temperature (T c ) of 1.54 K. This material is the first reported noncentrosymmetric superconductor that contains Au as a principal constituent element [24]. The electronic properties of SrAuSi 3 have been studied by means of the full-potential linearized augmented plane wave (FLAPW) employing a generalized gradient approximation of the density functional theory [24].…”

“…The electronic properties of SrAuSi 3 have been studied by means of the full-potential linearized augmented plane wave (FLAPW) employing a generalized gradient approximation of the density functional theory [24]. The spin-orbit interaction is included as a perturbation to the scalar-relativistic equations.…”

“…With this in mind, in this work, we have investigated the structural and electronic properties of SrAuSi 3 and SrAu 2 Si 2 using the ab initio pseudo-potential method based on a generalized gradient approximation of the density functional theory [36]. The calculated lattice and internal parameters for both materials are compared with their experimental values [24,25]. Details of the electronic band structure and the electronic density of states near the Fermi energy are presented and discussed.…”