Field Dependence of Electronic Specific Heat in Two-Band Superconductors

Abstract

The vortex structure is studied in light of MgB$_2$ theoretically based on a two-band superconducting model by means of Bogoliubov-de Gennes framework. The field dependence of the electronic specific heat coefficient $γ(H)$ is focused. The exponent $α$ in $γ(H)\propto H^α$ is shown to become smaller by adjusting the gap ratio of the two gaps on the major and minor bands. The observed extremely small value $α\sim 0.23$ could be explained reasonably well in this two-band model with the gap ratio $\sim 0.3$.