Strong Coupling Superconductivity in Ca-Intercalated Bilayer Graphene on SiC.

Wang, Xutao; Liu, Ningning; Wu, Yanfu; Qu, Yueqiao; Zhang, Wenxuan; Wang, Jinyue; Guan, Dandan; Wang, Shiyong et al. · Nano Lett · 2022

basic_science · Level V

Where this comes from

Abstract

The metal-intercalated bilayer graphene has a flat band with a high density of states near the Fermi energy and thus is anticipated to exhibit an enhanced strong correlation effect and associated fascinating phenomena, including superconductivity. By using a self-developed multifunctional scanning tunneling microscope, we succeeded in observing the superconducting energy gap and diamagnetic response of a Ca-intercalated bilayer graphene below a critical temperature of 8.83 K. The revealed high value of gap ratio, 2Δ/<i>k</i><sub>B</sub><i>T</i><sub>c</sub> ≈ 5.0, indicates a strong coupling superconductivity, while the variation of penetration depth with temperature and magnetic field indicates an isotropic <i>s</i>-wave superconductor. These results provide crucial experimental clues for understanding the origin and mechanism of superconductivity in carrier-doped graphene.