Electronic Structure and Properties of SrAlGe and BaAlGe

TL;DR

This study investigates the electronic structures of superconductors BaAlGe and SrAlGe using first principles calculations, revealing differences in Fermi surface topology and their relation to superconducting properties.

Contribution

It provides a detailed comparison of the electronic structures and Fermi surfaces of BaAlGe and SrAlGe, highlighting their topological differences and implications for superconductivity.

Findings

BaAlGe has two distinct Fermi surfaces with different dimensional characters.

SrAlGe has a single connected Fermi surface.

Higher T_c in SrAlGe is linked to Fermi surface topology and band dispersion differences.

Abstract

The electronic structures of BaAlGe and SrAlGe which are superconductors with hexagonal honeycomb layers have been studied by using a first principles method. Energy bands, Fermi surafces, and density of states are presented. The two materials have topologically different Fermi surfaces. BaAlGe has two Fermi surfaces: One has a three dimensional spinning-top-like shape and the other has a cylindrical shape with two dimensional character. SrAlGe has only one connected Fermi surface. Two gap superconductivity for BaAlGe is suggested from the inherently different character of the two Fermi surfaces. The higher $T_c$ of SrAlGe than BaAlGe is related to the difference in both the topology of the Fermi surface and the band dispersions along the $z$ direction.