How a Superconductor Broke the Record
Hydrogen-dense materials known as superhydrides can superconduct near room temperature—provided they are subjected to pressures above 150 gigapascals (GPa). Now Yanming Ma at Jilin University in China and colleagues have explained why one of those superhydrides, LaSc2H24, outperforms the best runner-up, LaH10 [1].
LaSc2H24 and LaH10 are metal clathrate superhydrides: Their unit cells consist of metallic elements surrounded by cages of hydrogen ions. This class of superconductor came to prominence in 2019 when LaH10 was shown to superconduct at the then-record temperature of 250–260 K (see Viewpoint: Pushing Towards Room-Temperature Superconductivity). Soon after, Ma and colleagues calculated that LaSc2H24 should go even higher, a prediction that was borne out when his team synthesized the compound and measured a critical temperature Tc of 298 K at 260 GPa. Despite this success, the theoretical tool that the researchers used to make their prediction did not elucidate why the additional scandium atoms in LaSc2H24 have the effect that they do.
To solve this mystery, Ma and colleagues studied LaSc2H24 using a more sophisticated model. The Tc below which LaH10 becomes a superconductor, though high, is limited by an anisotropy in the material’s electronic band structure that opens two different superconducting channels with two different values of Tc. The team found that the scandium atoms in LaSc2H24 modify this electronic structure via their 3d orbitals, which provide bridges that connect the 1s orbitals of the hydrogen atoms. This bridging provides a continuous pathway for electron transport, which makes the band structure more isotropic and unifies the two gaps. The scandium atoms also distort and soften the H–H bonds, which raises Tc by strengthening the quantized lattice vibrations that sustain the superconducting state. Next, the researchers will try to synthesize the related compound La2ScH36, which they predict could have an even higher Tc.
–Marric Stephens
Marric Stephens is a Corresponding Editor for Physics Magazine based in Bristol, UK
References
- Z. Wang et al., “Isotropic superconductivity in the room-temperature superconductor LaSc2H24,” Phys. Rev. B 114, 154501 (2026).