Predicted High-Temperature Superconductivity in Rare Earth Hydride ErH_2 at Moderate Pressure

Hydrides offer an opportunity to study high critical temperature (high-T_\rm c) superconductivity at experimentally achievable pressures. However, the pressure needed remains extremely high. Using density functional theory calculations, herein we demonstrate that a new rare earth hydride ErH_2 could be superconducting with T_\rm c \sim 80 K at 14.5 GPa, the lowest reported value for compressed hydrides to date. Intriguingly, due to Kondo destruction, superconductivity was prone to exist at 15 GPa. We also reveal an energy gap at 20 GPa on the background of normal metallic states. At 20 GPa, this compressed system could act as a host of superconductor judged from a sharp jump of spontaneous magnetic susceptibility with an evanescent spin density of state at Fermi level. Finally, electron pairing glue for ErH_2 at these three typical pressures was attributed to the antiferromagnetic spin fluctuation.