Ma Liang, Wang Kui, Xie Yu, Yang Xin, Wang Yingying, Zhou Mi, Liu Hanyu, Yu Xiaohui, Zhao Yongsheng, Wang Hongbo, Liu Guangtao, Ma Yanming
State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China.
International Center of Computational Method and Software, College of Physics, Jilin University, Changchun 130012, China.
Phys Rev Lett. 2022 Apr 22;128(16):167001. doi: 10.1103/PhysRevLett.128.167001.
The recent discovery of superconductive rare earth and actinide superhydrides has ushered in a new era of superconductivity research at high pressures. This distinct type of clathrate metal hydrides was first proposed for alkaline-earth-metal hydride CaH_{6} that, however, has long eluded experimental synthesis, impeding an understanding of pertinent physics. Here, we report successful synthesis of CaH_{6} and its measured superconducting critical temperature T_{c} of 215 K at 172 GPa, which is evidenced by a sharp drop of resistivity to zero and a characteristic decrease of T_{c} under a magnetic field up to 9 T. An estimate based on the Werthamer-Helfand-Hohenberg model gives a giant zero-temperature upper critical magnetic field of 203 T. These remarkable benchmark superconducting properties place CaH_{6} among the most outstanding high-T_{c} superhydrides, marking it as the hitherto only clathrate metal hydride outside the family of rare earth and actinide hydrides. This exceptional case raises great prospects of expanding the extraordinary class of high-T_{c} superhydrides to a broader variety of compounds that possess more diverse material features and physics characteristics.
最近超导稀土和锕系超氢化物的发现开启了高压下超导研究的新时代。这种独特类型的笼形金属氢化物最初是针对碱土金属氢化物CaH₆提出的，然而，长期以来一直未能通过实验合成，这阻碍了对相关物理性质的理解。在此，我们报告成功合成了CaH₆，并在172 GPa下测得其超导临界温度Tc为215 K，这通过电阻率急剧降至零以及在高达9 T的磁场下Tc的特征性下降得到证明。基于韦特哈默 - 赫尔方德 - 霍恩贝格模型的估计给出了203 T的巨大零温上临界磁场。这些卓越的基准超导特性使CaH₆跻身于最杰出的高Tc超氢化物之列，使其成为迄今为止稀土和锕系氢化物家族之外唯一的笼形金属氢化物。这一特殊情况为将高Tc超氢化物这一非凡类别扩展到具有更多样化材料特性和物理特征的更广泛化合物种类带来了巨大前景。
