Superconductivity in CaH 6 and ThH 10 through fully ab initio Eliashberg method and self-consistent Green's function.

Abstract

Pressurized hydrogen-based superconductors are phonon-mediated superconductors that exhibit high phonon frequencies. In these superconductors, in addition to the density of states (DOS) at the Fermi energy ( E F ), the energy dependence of the DOS around E F becomes important for evaluating their transition temperature ( T c ). Systems with peak structures in the DOS around E F , such as I m 3 ¯ m H 3 S and F m 3 ¯ m LaH 10 , highlight this point. We use the fully ab initio Eliashberg method to investigate this phenomenon in I m 3 ¯ m CaH 6 and F m 3 ¯ m ThH 10 with a dip structure in their DOS around E F . Our calculated T c values (225-235 K for CaH 6 at 200 GPa and 156-158 K for ThH 10 at 170 GPa) are quantitatively consistent with the experimental results. Remarkably, our results from the self-consistent treatment of the electron Green's function contrasts with those cases with a peak structure in the DOS. This finding unifies the understanding of how DOS structures influence the evaluation of T c .