NONLINEAR DIAMAGNETIC RESPONSE IN MESOSCOPIC RINGS OF SUPERCONDUCTORS ABOVE TC

We study the nonlinear diamagnetic response of mesoscopic rings of super-conductors above the transition temperature. Based on the standard expression for the fluctuation correction to the grand potential, OMEGA, we investigate the flux and temperature dependence of the equilibrium current I = - partial-OMEGA/partial-PHI, for the cases where T(c) is A) much smaller, and B) comparable to the coherence temperature T1 = hD/L2 (D is the diffusion constant, and L the circumference of the ring). The results are compared with, and contrasted to, recent experimental and theoretical studies of mesoscopic normal metal rings. New experiments are suggested for the easily achievable situation T(c) > T(1).