SUPERCONDUCTING MESOSCOPIC SQUARE LOOPS - PHASE BOUNDARIES AND MAGNETIZATION

For a superconducting mesoscopic square loop of intermediate size, com parable with the coherence length and with the penetration depth, the superconducting state is described and the phase boundaries are analyz ed on the basis of a self-consistent solution of the Ginzburg-Landau e quations. As a heuristic criterion for the phase boundary, the appeara nce of a ''superconducting path'' between the links of the leads with the loop is proposed in fair agreement with experiment. The magnetizat ion, deduced for states away from the phase boundary, reveals a quasi- oscillating behaviour. as a function of the applied magnetic field.