Scientists from Skoltech and their collaborators from China have experimentally demonstrated the occurrence of superconductivity in cerium superhydrides CeH9 and CeH10.
Structure of cerium superhydride CeH10 synthesized by the researchers and shown to be a high-temperature superconductor. Image Credit: Pavel Odinev/Skoltech.
The study, published in the Physical Review Letters journal, paves the way for lower pressure and potentially room-temperature superconductors. The path towards superconductivity, a highly appealing physical property of certain materials that do not lose energy to heat due to their zero resistance, is challenging.
It necessitates either very low temperatures (of 135 K, or −138 °C, at the warmest) or very high pressure (in 2019, it was discovered that LaH10 turns superconducting at −23 °C and 1.7 million atmospheres; and in 2020, it was found that a S-C-H compound superconducts at +15 °C and 2.7 million atmospheres).
Researchers have been making efforts to “normalize” superconductors, searching for compounds exhibiting this property at close to room temperature and a slightly less terrifying pressure.
As a continuation of the long-time search combining theory with experiment, Skoltech Professor Artem R. Oganov and PhD student Dmitrii Semenok collaborated with the team of Professors Tian Cui, Xiaoli Huang (Jilin University), and PhD student Wuhao Chen. This team has exhibited superconductivity in CeH9, a cerium superhydride they discovered in early 2019, as well as in the newly produced CeH10.
According to the researchers, “Cerium hydrides are remarkable compounds. Stable and displaying high-temperature superconductivity at lower pressures than any other superhydrides (about 0.8 million atmospheres), they serve as an ideal starting point to further study the mechanism of superconductivity in these fascinating compounds, and design other superconductors, stable at even lower pressures.”
Earlier we established a remarkably close relationship between the periodic table and superconductivity of hydrides—and we believe it should apply not just to hydrides! Take La and Ce—they are neighbors in the periodic table and indeed both form high-temperature superconductors. However, there are differences: LaH10 superconducts at higher temperatures, while CeH10 is stable at lower pressures.
Artem R. Oganov, Professor, Skoltech
The researchers highlighted that binary hydrides are mostly analyzed at present.
Now we need to carefully think how to combine the elements to achieve higher-temperature superconductivity at lower pressures in ternary hydrides. We know which elements lead to higher-temperature superconductivity and begin to learn which lead to stability at lower pressures. These are the main notes, but it takes imagination to combine them in a melody.”
Dmitrii Semenok, PhD Student, Skoltech
Jilin University, Ningbo University, and the Center for High Pressure Science and Technology Advanced Research are the other organizations involved in this study.
Journal Reference:
Chen, W., et al. (2021) High-Temperature Superconducting Phases in Cerium Superhydride with a Tc up to 115 K below a Pressure of 1 Megabar. Physical Review Letters. doi.org/10.1103/PhysRevLett.127.117001.