High-Temperature Superconducting Phases in Cerium Superhydride with a Tc up to 115 K below a Pressure of 1 Megabar
| Autor: | Artem R. Oganov, Xiaoli Huang, Tian Cui, Xin Li, Wuhao Chen, Haiyun Shu, Dmitrii V. Semenok, Defang Duan |
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| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Physical Review Letters. 127 |
| ISSN: | 1079-7114 0031-9007 |
| Popis: | The discoveries of high-temperature superconductivity in ${\mathrm{H}}_{3}\mathrm{S}$ and ${\mathrm{LaH}}_{10}$ have excited the search for superconductivity in compressed hydrides, finally leading to the first discovery of a room-temperature superconductor in a carbonaceous sulfur hydride. In contrast to rapidly expanding theoretical studies, high-pressure experiments on hydride superconductors are expensive and technically challenging. Here, we experimentally discovered superconductivity in two new phases, $Fm\overline{3}m\text{\ensuremath{-}}{\mathrm{CeH}}_{10}$ (SC-I phase) and $P{6}_{3}/mmc\text{\ensuremath{-}}{\mathrm{CeH}}_{9}$ (SC-II phase) at pressures that are much lower ($l100\text{ }\text{ }\mathrm{GPa}$) than those needed to stabilize other polyhydride superconductors. Superconductivity was evidenced by a sharp drop of the electrical resistance to zero and decreased critical temperature in deuterated samples and in external magnetic field. SC-I has ${T}_{c}=115\text{ }\text{ }\mathrm{K}$ at 95 GPa, showing an expected decrease in further compression due to the decrease of the electron-phonon coupling (EPC) coefficient $\ensuremath{\lambda}$ (from 2.0 at 100 GPa to 0.8 at 200 GPa). SC-II has ${T}_{c}=57\text{ }\text{ }\mathrm{K}$ at 88 GPa, rapidly increasing to a maximum ${T}_{c}\ensuremath{\sim}100\text{ }\text{ }\mathrm{K}$ at 130 GPa, and then decreasing in further compression. According to the theoretical calculation, this is due to a maximum of $\ensuremath{\lambda}$ at the phase transition from $P{6}_{3}/mmc\text{\ensuremath{-}}{\mathrm{CeH}}_{9}$ into a symmetry-broken modification $C2/c\text{\ensuremath{-}}{\mathrm{CeH}}_{9}$. The pressure-temperature conditions of synthesis affect the actual hydrogen content and the actual value of ${T}_{c}$. Anomalously low pressures of stability of cerium superhydrides make them appealing for studies of superhydrides and for designing new superhydrides with stability at even lower pressures. |
| Databáze: | OpenAIRE |
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