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 ${\hat{I}}^3(H)$ is focused. The exponent $\hat{I}\pm$ in ${\hat{I}}^3(H)\propto H^{\hat{I}}\pm$ 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 $\hat{I}\pm \sim 0.23$ could be explained reasonably well in this two-band model with the gap ratio $\sim 0.3$.

5 pages, 4 figures, to be published in J. Phys. Soc. Jpn