Adiabatically developed local coherence in YBCO above T-c

AC susceptibility has been measured simultaneously in three different regio ns of YBCO ceramic samples, in the presence of a strong thermal gradient, i n order to pinpoint local perturbation. A local step-like perturbation, app lied in addition to the monotonic temperature decrease, produces a jump-lik e increase of the coherent region. The superconducting regions enlarge much faster than the propagation of the thermal waves. We suggest that the adia batic magnetic Aux jump reflect the creation of new coherent domains over T -c by stimulated correlation of the order parameter phase. (C) 2000 Publish ed by Elsevier Science Ltd.