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

Rare-earth polyhydrides formed under pressure are promising conventional superconductors, with the critical temperature ${T}_{c}$ in compressed ${\mathrm{LaH}}_{10}$ 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 ${\mathrm{REH}}_{n}$ ($n=8,9,10$) that can be stabilized below 400 GPa show that enhanced ${T}_{c}$ 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 ${\mathrm{LaH}}_{10}$ and ${\mathrm{CeH}}_{9}$, we suggest ${\mathrm{YbH}}_{10}$ and ${\mathrm{LuH}}_{8}$ as additional potential high-${T}_{c}$ superconducters. They form a ``second island'' of high-${T}_{c}$ superconductivity amongst the late lanthanide polyhydrides, with an estimated ${T}_{c}$ of 102 K for ${\mathrm{YbH}}_{10}$ at 250 GPa.