Long-Term Stability of Superconducting Metal Superhydrides

TL;DR

This study demonstrates that LaH10 superhydride remains stable and retains its superconducting properties for over five years under high-pressure conditions, challenging previous assumptions about its long-term stability.

Contribution

It provides the first long-term experimental evidence of the stability of LaH10 superhydride at high pressure, supported by both experimental data and quantum chemistry predictions.

Findings

LaH10 is thermodynamically more stable than LaH3 under formation conditions.

LaH10 maintains its crystal structure and superconductivity for over five years.

Experimental results align with quantum chemistry stability predictions.

Abstract

Zhou et al., in their recent publication (Nat. Commun. 16, 1135, 2025), reported the synthesis of lanthanum superhydride, LaHx (x = 10.2-11.1), by laser heating LaH3 with NH3BH3 at a pressure of 170 GPa and investigated the temporal evolution of the NMR spectra of the reaction products. They observed a gradual decrease in the 1H-NMR signal intensity assigned to the synthesized metal hydride, accompanied by an increase in molecular hydrogen within the sample chamber over a period of 50 days. Based on these observations, the authors concluded that LaH10 progressively decomposes into LaH3 and H2 within two months after synthesis at its formation pressure of 170 GPa. Here, we demonstrate that, under their formation conditions, metal superhydrides are thermodynamically more stable than metal trihydrides. Furthermore, we present direct experimental evidence - based on X-ray diffraction and four-probe electrical resistance measurements - confirming the stability of both the crystal lattice and high-temperature superconducting properties of the Fm-3m-LaH10 phase for more than five years. This long-term stability is consistent with predictions from quantum chemistry calculations.