Strong coupling superconductivity in trilayer film LiB$_2$C$_2$

TL;DR

This paper predicts that trilayer film LiB$_2$C$_2$ is a promising high-temperature superconductor mediated by strong electron-phonon coupling, with a T$_c$ exceeding 77 K at ambient pressure and potentially reaching 125 K under strain.

Contribution

It introduces trilayer LiB$_2$C$_2$ as a new candidate for high-T$_c$ superconductivity based on first-principles calculations and anisotropic Eliashberg theory.

Findings

T$_c$ exceeds liquid-nitrogen temperature at ambient pressure.

T$_c$ can be increased to 125 K with biaxial tensile strain.

Strong coupling between $\sigma$-bonding electrons and phonons is key.

Abstract

Coupling between $\sigma$-bonding electrons and phonons is generally very strong. To metallize $\sigma$-electrons provides a promising route to hunt for new high-T$_c$ superconductors. Based on this picture and first-principles density functional calculation with Wannier interpolation for electronic structure and lattice dynamics, we predict that trilayer film LiB$_2$C$_2$ is a good candidate to realize this kind of high-T$_c$ superconductivity. By solving the anisotropic Eliashberg equations, we find that free-standing trilayer LiB$_2$C$_2$ is a phonon-mediated superconductor with T$_c$ exceeding the liquid-nitrogen temperature at ambient pressure. The transition temperature can be further raised to 125 K by applying a biaxial tensile strain.