Potential high- T c superconducting lanthanum and yttrium hydrides at high pressure

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 114; no. 27; pp. 6990 - 6995
• Main Authors: Liu, Hanyu, Naumov, Ivan I., Hoffmann, Roald, Ashcroft, N. W., Hemley, Russell J.
• Format: Journal Article
• Language: English
• Published: United States Proceedings of the National Academy of Sciences 03.07.2017
• Subjects: CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; high pressure; hydrides; structure search; superconductivity; hydrides; superconductivity; structure search; high pressure
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1704505114

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, LaH 10 is found to adopt a sodalite-like face-centered cubic (fcc) structure, stable above 200 GPa, and LaH 8 a C 2/ 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- T c superconductors. In particular, the superconducting transition temperature T c calculated for LaH 10 is 274–286 K at 210 GPa. Similar calculations for the Y–H system predict stability of the sodalite-like fcc YH 10 and a T c 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.