First-principles Calculation of Superconductivity in Hole-doped LiBC: $T_c=65$ K

Abstract

The lattice dynamical properties of Li${}_x$BC are calculated for several values of $x$ using density functional perturbation theory. We find that the electron-phonon coupling parameter $\hat{I}»$ increases monotonically with decreasing $x$ to a maximum value of 1.4 for $x=0.125$ owing to the increasing radius of multiply-nested Fermi surface cylinders. The B-C bond-stretching phonon modes have frequencies which are 28% higher than the equivalent modes in MgB${}_2$. This combination results in a $T_c$ of about 65 K for $x=0.5$.

6 pages, 5 figures