Discontinuity of capacitance at the onset of surface superconductivity

The effect of magnetic field on a capacitor with a superconducting electrode is studied with the Ginzburg-Landau approach. It is shown that the capacitance has a discontinuity at the onset of the surface superconductivity, which is expressed as a discontinuity in the depth of penetration of the electric field into metals. This new effect establishes a macroscopic signal of the onset of superconducting correlations. This discontinuity is observable with recent bridges for both conventional and high-Tc superconductors.