Electronic structure of new superconductor La0.5Th0.5OBiS2: DFT study

Abstract

We studied from first-principles the recently discovered BiS2-layered superconductor La0.5Th0.5OBiS2 and compared with LaO0.5F0.5BiS2. Firstly, we have performed a global geometry optimization in order to predict an accurate ground state. In contract to the parent semiconductor LaOBiS2 and according to other recent works, the band structure of both materials presents superconducting behavior, four bands of Bi-6p orbitals that cross a Fermi-level. Additionally, the systematic study of the electronic properties as a function of pressure shows the same behavior in both materials “Enhancement of superconductivity TC”, where the Fermi-level is shifted upward and the Fermi surface presents a similar dispersion. These similarities between tetravalent cation electron-doped via Th+4 substitution for La+3 (La0.5Th0.5OBiS2), and monovalent anion electron-doped via F− substitution for O2− (LaO0.5F0.5BiS2) may predict the same electronic properties.