Superconductivity in Ca-intercalated bilayer graphene: C$_{2}$CaC$_{2}$

Jin-Han Tan; Hao Wang; Ying-Jie Chen; Na Jiao; Meng-Meng Zheng; Hong-Yan Lu; Ping Zhang

doi:10.1039/d3cp06245g

paper

Superconductivity in Ca-intercalated bilayer graphene: C $_{2}$ CaC $_{2}$

arXiv:2312.01363 · doi:10.1039/d3cp06245g

Abstract

The deposition and intercalation of metal atoms can induce superconductivity in monolayer and bilayer graphenes. For example, it has been experimentally proved that Li-deposited graphene is a superconductor with critical temperature $T_{c}$ of 5.9 K, Ca-intercalated bilayer graphene C $_{6}$ CaC $_{6}$ and K-intercalated epitaxial bilayer graphene C $_{8}$ KC $_{8}$ are superconductors with $T_{c}$ of 2-4 K and 3.6 K, respectively. However, the $T_{c}$ of them are relatively low. To obtain higher $T_{c}$ in graphene-based superconductors, here we predict a new Ca-intercalated bilayer graphene C $_{2}$ CaC $_{2}$ , which shows higher Ca concentration than the C $_{6}$ CaC $_{6}$ . It is proved to be thermodynamically and dynamically stable. The electronic structure, electron-phonon coupling (EPC) and superconductivity of C $_{2}$ CaC $_{2}$ are investigated based on first-principles calculations. The EPC of C $_{2}$ CaC $_{2}$ mainly comes from the coupling between the electrons of C- $p_{z}$ orbital and the high- and low-frequency vibration modes of C atoms. The calculated EPC constant $λ$ of C $_{2}$ CaC $_{2}$ is 0.75, and the superconducting $T_{c}$ is 18.9 K, which is much higher than other metal-intercalated bilayer graphenes. By further applying -4\% biaxial compressive strain to C $_{2}$ CaC $_{2}$ , the $T_{c}$ can be boosted to 26.6 K. Thus, the predicted C $_{2}$ CaC $_{2}$ provides a new platform for realizing superconductivity with the highest $T_{c}$ in bilayer graphenes.

29 pages,11 figures

Superconductivity in Ca-intercalated bilayer graphene: C2​CaC2​

Abstract

Superconductivity in Ca-intercalated bilayer graphene: C $_{2}$ CaC $_{2}$