Boundary Effect of Two-Band Superconductors and Its Impact on the Critical Temperature of MgB2 Thin Film

Abstract

Based on two-band Bogoliubov-de Gennes theory, we study the boundary effect of an interface between two-band superconductor and insulator (or vacuum). New boundary terms are introduced into two-band Ginzburg-Landau free energy, and the characteristic length scale of boundary effect can be estimated. Taking into account this boundary effect, we study the critical temperature dependence of film thickness for magnesium diboride. Our numerical results are in good agreement with the experimental data measured in this material.