Potential high Tc superconducting lanthanum and yttrium hydrides at high pressure
Significance Theoretical predictions and subsequent experimental observations of high temperature superconductivity in dense hydrogen rich compounds have reinvigorated the field of superconductivity. A systematic computational study of the hydrides of lanthanum and yttrium over a wide composition range reveals hydrogen rich structures with intriguing electronic properties under pressure. Electron phonon coupling calculations predict the existence of new superconducting phases, some exhibiting superconductivity in the range of room temperature. Moreover, the calculated stabilities indicate the materials could be synthesized at pressures that are currently accessible in the laboratory. The results open the prospect for the design, synthesis, and recovery of new high temperature superconductors with potential practical applications. A systematic structure search in the La H and Y H systems under pressure reveals some hydrogen rich structures with intriguing electronic properties. For example, LaH10 is found to adopt a sodalite like face centered cubic (fcc) structure, stable above 200 GPa, and LaH8 a C2/m space group structure. Phonon calculations indicate both are dynamically stable; electron phonon calculations coupled to Bardeen Cooper Schrieffer (BCS) arguments indicate they might be high Tc superconductors. In particular, the superconducting transition temperature Tc calculated for LaH10 is 274 286 K at 210 GPa. Similar calculations for the Y H system predict stability of the sodalite like fcc YH10 and a Tc above room temperature, reaching 305 326 K at 250 GPa. The study suggests that dense hydrides consisting of these and related hydrogen polyhedral networks may represent new classes of potential very high temperature superconductors.
Proceedings of the National Academy of Sciences