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O: Fachverband Oberflächenphysik

O 17: Mini-Symposium: Frontiers of electronic-structure theory: Focus on electron-phonon interactions I

O 17.2: Invited Talk

Monday, March 1, 2021, 14:00–14:30, R3

Huge quantum effects on the 250 K superconducting lan- thanum hydride — •Ion Errea — University of the Basque Country, San Sebastian, Spain

The discovery of superconductivity at 200 K in the hydrogen sulfide system at large pressures was a clear demonstration that hydrogen-rich materials can be high-temperature superconductors. The recent syn- thesis of LaH10 with a superconducting critical temperature (Tc) of 250 K place these materials at the verge of reaching the long-dreamed room-temperature superconductivity. Here we show that quantum atomic fluctuations stabilize in the superconducting pressure range a high-symmetry Fm-3m crystal structure consistent with experiments, which has a colossal electron-phonon coupling of 3.5. Even if ab initio classical calculations predict this structure to distort below 230 GPa yielding a complex energy landscape, the inclusion of quantum effects evidences the Fm-3m as the true ground state. The agreement be- tween the calculated and experimental Tc values further supports this phase as responsible for the 250 K superconductivity. The relevance of quantum fluctuations questions many of the crystal structure predic- tions made for hydrides within a classical approach that at the moment guide the experimental quest for room-temperature superconductivity. Furthermore, quantum effects are revealed to be crucial to stabilize solids with extraordinary electron-phonon coupling, which may other- wise be destabilized by the large electron-phonon interaction, reducing the pressures needed for their synthesis.