Superconductivity in graphite intercalation compounds with sodium

TL;DR

This paper reports the discovery of NaC4, a sodium graphite intercalation compound with a predicted superconducting transition temperature of 41.2 K at 5 GPa, significantly higher than previously known GICs, due to electron-phonon coupling.

Contribution

The study identifies NaC4 as a high-Tc superconductor through ab initio calculations, expanding the understanding of superconductivity in GICs with sodium intercalation.

Findings

NaC4 has a predicted Tc of 41.2 K at 5 GPa.

NaC4's superconductivity arises from coupling of graphene π electrons with low-frequency vibrations.

Na-GICs may be promising high-temperature superconductors.

Abstract

The discovery of superconductivity in CaC6 with a critical temperature (Tc) of 11.5 K reignites much interest in exploring high-temperature superconductivity in graphite intercalation compounds (GICs). Here we identify a GIC NaC4, discovered by ab initio evolutionary structure search, as a superconductor with a computed Tc of 41.2 K at 5 GPa. This value is eight times higher than that of the synthesized GIC NaC2 and possesses the highest Tc among available GICs. The remarkable superconductivity of GIC NaC4 mainly arises from the coupling of {\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-Tc superconductors.