Superconducting properties of rare-earth boron hydrides at high pressure studied by first-principles calculations

It is a long-thought proposal that dense light-element molecular hydrides, such as diborane (B2H6) and methane (CH4), offer an ideal platform to search for phonon-mediated superconductors. However, these hydrides are often unstable under sufficiently high pressure, e.g., B2H6 decomposed into BH and H2 at pressures of above 153 GPa, which are unlikely to exhibit high superconductivity. Here, we find a feasible route to stabilize these light-element molecular hydrides with high superconductivity under high pressure by high-throughput structure searches and first-principles calculations. We uncover a series of stable H-rich rare-earth (R) metal based boron hydrides RB2H10 with polydiborane networks. Strikingly, YB2H10 is predicted to be a high-temperature superconductor with unprecedentedly critical temperature (Tc) of up to 93 K under 150 GPa. The present findings open a route to stabilize the unstable diborane by bringing the additional R metals into the lattice under high pressure, as well as tuning the superconductivity among diborane-based hydrides and other similar dense light-element molecular hydrides.