Electronic band structure, Fermi surface and elastic properties of polymorphs of new 5.2K iron-free superconductor SrPt2As2 from first principles calculations

TL;DR

This study uses first-principles calculations to analyze the structural, electronic, and elastic properties of a new 5.2K superconductor SrPt2As2 and its polymorphs, revealing unique Fermi surface features and stability characteristics.

Contribution

It provides detailed insights into the electronic structure and stability of different SrPt2As2 polymorphs, highlighting the unique properties of the CaBe2Ge2-type structure.

Findings

CaBe2Ge2-type SrPt2As2 has a complex 2D-3D Fermi surface topology.

The CaBe2Ge2-type is mechanically stable, soft, and ductile.

ThCr2Si2-type polymorphs are less stable with high elastic anisotropy.

Abstract

By means of the first-principles calculations, we have studied in details the structural, elastic and electronic properties of the new tetragonal CaBe2Ge2-type 5.2K superconductor SrPt2As2 in comparison with two hypothetical SrPt2As2 polymorphs with ThCr2Si2-type structures which differ by atomic configurations of [Pt2As2] (or [Pt2As2]) blocks. We have found that CaBe2Ge2-type SrPt2As2 is a quite unique system with complicated 2D-3D character of near-Fermi bands, and the "intermediate" type of the Fermi surface, which consists of electronic pockets having cylinder-like (2D) topology (typical for 122 FeAs phases) together with 3D-like electronic and hole pockets, which are characteristic for ThCr2Si2-like iron-free low-Tc superconductors. Our analysis reveals that against ThCr2Si2-like 122 phases, the other features for CaBe2Ge2-like SrPt2As2 are: (1). The essential differences of contributions of states from [Pt2As2] and [Pt2As2] blocks into near-Fermi region when the conduction is expected to be anisotropic and happening mainly in [Pt2As2] blocks; (2). The formation of the 3D system of strong covalent Pt-As bonds (inside and between of [Pt2As2]/[As2Pt2] blocks) which is responsible for enhanced stability of this polymorph, and (3). the essential charge anisotropy between the adjacent [Pt2As2] and [As2Pt2] blocks. We have predicted also that CaBe2Ge2-like SrPt2As2 is mechanically stable, relatively soft material with high compressibility and will behave in a ductile manner. On the contrary the ThCr2Si2-type SrPt2As2 polymorphs which contain only [Pt2As2] or [As2Pt2] blocks, are less stable, their Fermi surfaces adopt a multi-sheet three-dimensional type - similar to ThCr2Si2-like iron-free 122 phases, and these polymorphs will be ductile materials with high elastic anisotropy.