Stable cerium hydrides are steps in route to room-temperature superconductors

Researchers are hunting for materials that become superconducting at room temperature, which would allow the efficient energy transport properties of superconductors to be more widely applied.

In the search for room-temperature superconductors, Li et al. explored possible crystal structures of the cerium-hydride (Ce-H) system under the pressure range from 0 to 300 GPa. The properties of hydrogen-rich hydrides suggest they might have high superconductivity critical temperatures — the temperature at which a material's electrical resistance drops to zero and becomes superconducting.

Using an evolutionary crystal structure prediction algorithm, the authors predicted the existence of three new stable phases for the binary compound: CeH₄, CeH₉, and CeH₁₀. Previous studies have examined hexagonal CeH₉ and rhombohedral CeH₁₀. The authors found, however, that CeH₉ and CeH₁₀ prefer cubic symmetry.

They calculated the maximum superconductivity critical temperature for cubic CeH₉ and CeH₁₀ to be 142 K and 168 K respectively, much higher than previously reported values. The transition of CeH₉ and CeH₁₀ to superconductivity also occurred at pressures lower than 100 GPa.

The predicted high superconductivity critical temperatures of these structures at experimentally-attainable pressures could help lead researchers to a hydrogen-rich room-temperature superconductor.

“In the future, the realization of a room-temperature superconductor under ambient pressure will profoundly affect the way humans use energy,” said author Bin Li. Next in their search, the authors will examine ternary hydrides in the cerium system.

“Maybe we can also explore broader areas not limited to the hydrides, like the possibility of superconductivity in lithium-sulfur compounds,” Li said.

Source: “Predicted high-temperature superconductivity in cerium hydrides at high pressures,” by Bin Li, Zilong Miao, Lei Ti, Shengli Liu, Jie Cheng, Zhixiang Shi, and Eugene Gregoryanz, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5130583.