Superconductivity in sodalite-like yttrium hydride clathrates*

Motivated by the discovery of near-room-temperature superconductivity in the sodalite-like clathrate hydride LaH10, we report ab initio calculations of the superconducting properties of two closely related hydrides YH6 and YH10 [1], for which an even higher Tc has been predicted. Using fully anisotropic Migdal-Eliashberg theory with Coulomb corrections, we find almost isotropic superconducting gaps, resulting from a uniform distribution of the coupling over states of both Y and H sublattices. The Coulomb screening is rather weak, resulting in a Morel-Anderson pseudopotential μ* = 0.11, at odds with claims of unusually large μ* in lanthanum hydrides. The corresponding critical temperatures at 300 GPa exceed room temperature (Tc = 290 and 310 K for YH6 and YH10), in agreement with a previous isotropic-gap calculation. We estimate anharmonic effects to be weak.

[1] C. Heil, et al., Phys. Rev. B 99, 220502(R) (2019)