Magnetic Field Dependence of the Energy Gap in Superconductors

Abstract

We calculate the reduction of the energy gap at zero temperature for a bulk superconductor in the presence of a static external magnetic field, to the second order in the field strength. Simple formulas are obtained for the long ($\lambda \gg {\xi }_0$) and short ($\lambda \ll {\xi }_0$) wavelength limits, where ${\xi }_0$ is the coherence length.