Science1 publisher2 min readPublished
Physicists trace a predicted room-temperature hydride superconductor to scandium's 3d electrons
Jilin and Zhejiang physicists say scandium's 3d electrons explain why the predicted hydride LaSc2H24 should superconduct at 43 degrees Celsius. The account points hydride searches toward partly filled 3d orbitals, though the compound would still need 167 GPa of pressure.
The Scientist · Science desk
What happened
- LaH10, whose superconductivity was announced in 2018, works at up to minus 13 degrees Celsius but only under 188 GPa of pressure.
- The team traces LaH10's ceiling to band-structure anisotropy that opens two superconducting channels with different critical temperatures.
- Scandium's 3d orbitals overlap strongly with the hydrogen cages and reshape the Fermi surface to favour some Sc-H-Sc bonds over others.
- Swapping scandium for calcium, whose 3d orbital is empty, or magnesium, which has none, gave stable materials that did not superconduct.
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Why it matters
- contradiction phys.org's lead says the superconductor was confirmed, but its headline calls it predicted and the authors call the paper a theoretical blueprint, so the 56-degree gain over LaH10 compares a calculation with a reported discovery.
- decision Computational searches for hydrides that beat LaH10 now have a criterion to test first, partly filled 3d orbitals overlapping the hydrogen cage, though two knockouts do not show how much more 3d occupancy would add.
- constraint The explanation addresses the predicted critical temperature and leaves the pressure requirement in place: at 167 GPa, about 1.7 million atmospheres, LaSc2H24 is no closer to use at ordinary pressures.
Next to LaH10, the 2024 prediction puts LaSc2H24's critical temperature 56 degrees higher, at 21 GPa less pressure [1][2]. phys.org calls that "slightly better" [7]. The comparison also puts a calculation beside a reported discovery. LaH10's superconductivity was announced in a 2018 preprint and published in Nature half a year later [4]. LaSc2H24's 43 degrees Celsius at 167 GPa comes from a prediction [7]. phys.org's opening line says scientists "have confirmed the existence of a predicted room temperature superconductor" [3]. The authors call their paper "a theoretical blueprint for the future design of superior superconductor hydrides" [2]. The account does not describe anyone making and measuring a sample of LaSc2H24, or of the variants tested.
The Jilin and Zhejiang group started from a question the prediction left open. The tools behind it did not say why adding two scandium atoms would change LaH10's behaviour so much [15][1]. In LaSc2H24, lanthanum sits fully inside a cage of 30 hydrogen atoms, while scandium sits partly inside cages of 24 [11]. The group gives scandium's effect on LaH10's two-channel picture a name. "Our findings identify this Sc-induced gap unification as the fundamental mechanism," the group said [14].
The calcium and magnesium swaps are the part of the design I like best [13]. The group kept the lattice stable and took the 3d electrons away, once with an empty 3d orbital and once with none. Superconductivity survived neither change [13]. On that evidence, the hydrogen cage alone does not produce the effect.
The thing this doesn't tell you is how far 3d electrons can push the critical temperature. Two knockouts show the electrons are necessary in this analysis. They do not show how critical temperature changes as 3d occupation rises, and a design rule for beating LaH10 needs that relationship.
I think the blueprint mostly helps computational screening, where the question is which metal to put in the cage. It does less for anyone who wants a conductor they can use. Critical temperature is the figure these papers compete on. The obstacle to use is pressure. LaH10 superconducts only in a dense, metallic, hydrogen-rich phase that is stable at enormous pressures [6]. At 167 GPa, LaSc2H24 would still need roughly 1.7 million atmospheres [3].
The prediction and its explanation also share authors. Yanming Ma, who is affiliated with both universities, co-wrote both papers [8].
What to watch
- A synthesis and resistance measurement of LaSc2H24 by a group outside the Jilin-Zhejiang collaboration, reporting the pressure at which it superconducts.
- Calculations on other metals with partly filled 3d shells in the same cage structure, showing whether critical temperature tracks 3d occupation.
- Whether the gap-unification picture also accounts for LaSc2H24 needing 21 GPa less pressure than LaH10, or only for the temperature gain.