| LaH10 | |
|---|---|
| Name | LaH10 |
| Chemical formula | LaH10 |
| System | Cubic/Clathrate-like |
| Crystal system | Cubic (Fm-3m) and variants |
| Discovery date | 2018–2019 |
| Discovered by | Research groups at Max Planck Institute/University of Edinburgh/University of Chicago and collaborators |
| Critical temperature | up to ~250–260 K (reported) |
| Critical pressure | ~150–200 GPa |
| Type | Conventional phonon-mediated superconductor (strong-coupling) |
LaH10
LaH10 is a hydrogen-rich lanthanum hydride that attracted significant attention for its reported high-temperature superconductivity under extreme pressure conditions. It exemplifies the class of record-breaking hydride superconductors predicted by first-principles calculations and realized experimentally during the search for room-temperature superconductors. LaH10 matters in the context of Quantum Physics because its superconducting behavior probes fundamental aspects of electron–phonon coupling, Cooper pairing in dense hydrogenic lattices, and the limits of conventional Bardeen–Cooper–Schrieffer (BCS) theory and strong-coupling extensions such as Migdal–Eliashberg formalism.
LaH10 was reported with a stoichiometry approximating LaH10 and a clathrate-like hydrogen framework encapsulating lanthanum atoms. The most discussed phase crystallizes in the cubic space group Fm-3m with lanthanum occupying fcc positions and hydrogen forming a cagelike network similar to a sodalite or clathrate motif. Competing stoichiometries (e.g., LaH9, LaH11) and lower-symmetry distortions have been proposed; these variants affect the hydrogen sublattice topology and phonon spectrum. Structural determination has relied on X-ray diffraction and synchrotron radiation at megabar pressures, often combined with theoretical structure prediction methods such as USPEX and CALYPSO.
Electronic structure calculations indicate that LaH10 is metallic with a high electronic density of states at the Fermi level dominated by hydrogen-derived bands, which enhances electron–phonon coupling. Experimental reports claim superconducting critical temperatures (Tc) in excess of 250 K at pressures around 150–200 GPa; the superconducting state shows a large isotope effect upon substituting deuterium, consistent with phonon-mediated pairing. Measured properties include zero electrical resistance in diamond anvil cell transport measurements and shifts in magnetic susceptibility consistent with the Meissner effect, though the small sample volumes and extreme conditions complicate definitive bulk measurements. Key theoretical and experimental analyses reference Migdal–Eliashberg theory, phonons, and spectroscopic probes such as Raman spectroscopy and infrared spectroscopy.
LaH10 was first highlighted by high-throughput computational searches using density functional theory (DFT) and structure prediction algorithms. Studies applied the harmonic and anharmonic phonon calculations, Migdal–Eliashberg equations, and quantum Monte Carlo methods to estimate Tc and stability fields. Anharmonic effects and hydrogen quantum zero-point motion were shown to renormalize phonon frequencies and significantly influence superconducting coupling constants (λ). Prominent computational tools and approaches used include DFT, Quantum ESPRESSO, ab initio molecular dynamics, and Eliashberg calculations; notable contributors include researchers at institutions such as Massachusetts Institute of Technology, Max Planck Institutes, and George Washington University among others who pursued predictive modeling and validation against experiments.
Synthesis of LaH10 requires compressing a mixture of lanthanum and hydrogen (or a hydrogen source like ammonia borane) in a diamond anvil cell (DAC) to pressures typically above 100 GPa, often combined with laser heating to promote reaction and crystallization. Characterization employs synchrotron X-ray diffraction for structural identification, electrical transport for superconducting transitions, and magnetic measurements where feasible. Groups at institutions including Harvard University, University of Rochester, University of Chicago, and national laboratories have reported experimental observations. Challenges include controlling stoichiometry, differentiating surface and bulk effects, and reproducibility across independent laboratories.
LaH10 exhibits a pressure-dependent phase diagram where the cubic clathrate-like phase is stable over a finite high-pressure window; at lower pressures it decomposes to other hydrides or elemental phases. The superconducting Tc shows strong pressure dependence: some reports indicate maximal Tc near ~150–200 GPa with decreasing Tc upon compression beyond that range or upon decompression. Phase boundaries and metastability are influenced by temperature, chemical precursors, and kinetic pathways during synthesis. Mapping this diagram combines experimental DAC studies, equation-of-state measurements, and theoretical convex-hull calculations to predict thermodynamic stability against decomposition into LaH2/LaH3 and molecular hydrogen.
LaH10 represents a milestone in the pursuit of high-temperature superconductivity and validates computational materials design strategies. Its discovery has stimulated research across condensed matter physics, materials science, and quantum materials engineering, motivating searches for lower-pressure hydrides, chemical precompression strategies (e.g., alloying or chemical substitution), and improved theoretical treatments of strong-coupling superconductivity. Broader implications include potential routes toward ambient-condition superconductors and insights into hydrogen-dominant metallic systems relevant to planetary physics and high-pressure chemistry studied at facilities such as ESRF and SLAC. Continued cross-disciplinary work among theorists and experimentalists at universities and national laboratories remains central to resolving open questions about reproducibility, bulk superconducting fraction, and mechanisms in hydride superconductors.
Category:Superconductors Category:Lanthanum compounds Category:High-pressure chemistry