Dynamics and superconductivity in compressed lanthanum superhydride

Abstract

Recent computational studies have predicted that rare-earth superhydrides are promising high-temperature superconductors. Of these phases having very high hydrogen content (XHn, n > 6, where X is the rare-earth atom) a cubic phase of lanthanum hydride, recently synthesized at 170 GPa and identified as LaH10 +/- x, is in good agreement with theoretical predictions. The experiments found that the stability of the phase extended to lower pressure and a distorted form was found on decompression. Here we examine the nuclear quantum effects and anharmonic dynamics on LaH10, including the behavior of the hydrogen sublattice in comparison with the predicted atomic metallic hydrogen at higher pressure. We also examine the vibrational dynamics and electronic properties of a distorted lower pressure phase of LaH10 and find that superconducting Tc decreases relative to cubic but remains relatively high (i.e., 229-245 K).