Note on possibility of proximity induced spontaneous currents in superconductor/normal metal heterostructures

Abstract

We analyse the possibility of the appearance of spontaneous currents in proximated superconducting/normal metal (S/N) heterostructure when Cooper pairs penetrate into the normal metal from the superconductor. In particular, we calculate the free energy of the S/N structure. We show that whereas the free energy of the N film $F_N$ in the presence of the proximity effect increases compared to the normal state, the total free energy, which includes the boundary term $F_B$, decreases. The condensate current decreases $F_N$, but increases the total free energy making the current-carrying state of the S/N system energetically unfavorable.

6 pages, the anaylsis includes the contribution of the boundary to the free energy, absent in the previous version. The conclusions are modified