Prediction of superconducting properties of CaB2 using anisotropic Eliashberg theory

TL;DR

This study predicts that hypothetical CaB2 could exhibit higher superconducting transition temperatures and a more pronounced two-gap structure compared to MgB2, based on detailed anisotropic Eliashberg calculations.

Contribution

It applies fully anisotropic Eliashberg theory to predict superconducting properties of CaB2 from first-principles calculations, a novel approach for this compound.

Findings

CaB2 likely has higher Tc than MgB2

CaB2 exhibits a stronger two-gap superconductivity

The energy gap Delta(k) varies significantly between sigma and pi bands

Abstract

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 Delta(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 Delta(k) in the sigma bands but a smaller Delta(k) in the pi bands than MgB2.