Prediction of superconducting properties of CaB2 using anisotropic Eliashberg theory

Superconducting properties of hypothetical simple hexagonal CaB2 are studied using the fully anisotropic Eliashberg formalism based on electronic and phononic structures and electron-phonon interactions, which are obtained from ab initio pseudopotential density-functional calculations. The superconducting transition temperature Tc, the superconducting energy gap Δ (k) on the Fermi surface, and the specific heat are obtained and compared with corresponding properties of MgB2. Our results suggest that CaB2 will have a higher Tc and a stronger two-gap nature, with a larger Δ (k) in the σ bands but a smaller Δ (k) in the π bands than MgB2.