Superconductivity in compounds of sodium-intercalated graphite
Chun-Mei Hao, Xing Li, Artem R. Oganov, Jingyu Hou, Shicong Ding, Yanfeng Ge, Lin Wang, Xiao Dong, Hui‐Tian Wang, Guochun Yang, Xiang‐Feng Zhou, Yongjun Tian
Abstract
The discovery of superconductivity in $\mathrm{Ca}{\mathrm{C}}_{6}$ with a critical temperature (${T}_{c}$) of 11.5 K reignited much interest in exploring high-temperature superconductivity in graphite intercalation compounds (GICs). Here we identify a GIC $\mathrm{Na}{\mathrm{C}}_{4}$, discovered by ab initio evolutionary structure search, as a superconductor with a computed ${T}_{c}$ of 41.2 K at 5 GPa. This value is eight times higher than that of the synthesized GIC $\mathrm{Na}{\mathrm{C}}_{2}$ and possesses the highest ${T}_{c}$ among available GICs. The remarkable superconductivity of GIC $\mathrm{Na}{\mathrm{C}}_{4}$ mainly arises from the coupling of \ensuremath{\pi} electrons in graphene with the low-frequency vibrations involving both Na and C atoms. These findings suggest that Na GICs may hold great promise as high-${T}_{c}$ superconductors.