Second group of high-pressure high-temperature lanthanide polyhydride superconductors

Rare-earth polyhydrides formed under pressure are promising conventional superconductors, with the critical temperature Tc in compressed LaH₁₀ almost reaching room temperature. Here, we report a systematic computational investigation of the structural and superconducting properties of rare-earth (RE) polyhydrides formed under pressure across the whole lanthanide series. Analyses of the electronic and dynamical properties and electron-phonon coupling interaction for the most hydrogen-rich hydrides REHₙ ($n=8,9,10$) that can be stabilized below 400 GPa show that enhanced Tc correlates with a high density of H s states and low number of RE f states at the Fermi level. In addition to previously predicted and measured LaH₁₀ and CeH₉, we suggest YbH₁₀ and LuH₈ as additional potential high-Tc superconducters. They form a ``second island'' of high-Tc superconductivity amongst the late lanthanide polyhydrides, with an estimated Tc of 102 K for YbH₁₀ at 250 GPa.