ON THE SUPERCONDUCTING PHASE-BOUNDARY FOR A MESOSCOPIC SQUARE LOOP

A self-consistent solution of the Ginzburg-Landau equations for a meso scopic superconducting square loop has been obtained. It has been show n that the inhomogeneous distribution of the amplitude of the order pa rameter inside the loop leads to the appearance of certain areas where it is much more difficult to rotate the superconducting condensate an d which therefore sustain much higher applied magnetic fields. The int erplay between the square symmetry of the loop and the cylindrical sym metry of the magnetic field results in different oscillatory supercond ucting phase boundaries which correspond to various phase boundary def initions. The most ''realistic'' criterion to define the phase boundar y magnetic field(H)-temperature(T) is formulated; it allows to obtain a good agreement between the calculated H(T) curve and the experimenta lly observed one. Copyright (C) 1996 Elsevier Science Ltd