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 SrGe2-d shows superconductivity by high pressure synthesis. This compound attracts our attention because it has the highest T-c among AGe(2) 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.