Electronic Structure of Novel Binary Superconductor SrGe₂: A First-Principles Study

Due to the simplicity of its composition, many binary superconductors have been developed so far. Some are practically used like Nb₃Ge, and others have high T _c like MgB₂ or single layer FeSe. Recently we discovered that tetragonal SrGe_2-d shows superconductivity by high pressure synthesis. This compound attracts our attention because it has the highest T _c among AGe₂ series (A: alkaline-earth or rare-earth element). In this paper we investigated the electronic structure of SrGe₂ from first principles. There are several polymorphs of SrGe₂, and the obtained density of states at the Fermi level (=D(E _F)) per SrGe₂ is 1.00, 1.20, 1.12 eV^-1 for trigonal, hexagonal and tetragonal structure, respectively. D(E _F) of tetragonal SrGe₂ is not more than the isostructural and isovalent compound BaGe₂, which has lower T _c than SrGe₂. (paper)