Superconductivity in sodalite-like yttrium hydride clathrates

TL;DR

This study uses ab-initio calculations to analyze superconductivity in yttrium hydride clathrates YH6 and YH10, revealing near-isotropic gaps and critical temperatures exceeding room temperature at high pressure.

Contribution

First detailed anisotropic ME theory analysis of YH6 and YH10, showing uniform electron-phonon coupling and high Tc, challenging previous claims of larger Tc in similar hydrides.

Findings

Critical temperatures of 290 K and 310 K at 300 GPa

Weak Coulomb screening with mu* = 0.11

Isotropic superconducting gaps in both compounds

Abstract

We report ab-initio calculations of the superconducting properties of two high-Tc sodalite-like clathrate yttrium hydrides, YH6 and YH10, within the fully anisotropic ME theory, including Coulomb corrections. For both compounds we find almost isotropic superconducting gaps, resulting from a uniform distribution of the electron-phonon coupling over phonon modes and electronic states of mixed Y and H character. The Coulomb screening is rather weak, resulting in a Morel-Anderson pseudopotential mu*= 0:11, at odds with claims of unusually large Tc in lanthanum hydrides. The corresponding critical temperatures at 300 GPa exceed room temperature (Tc = 290 K and 310 K for YH6 and YH10), in agreement with a previous isotropic-gap calculation. The different response of these two compounds to external pressure, along with a comparison to low-Tc superconducting YH3, may inspire strategies to improve the superconducting properties of this class of hydrides.