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Driven Vortex States and Relaxation in Single Crystal YBa2Cu4O8

V. Metlushko, U. Welp, I. Aranson, S. Scheidl, V. M. Vinokur, G. W. Crabtree, K. Rogacki, B. Dabrowski

cond-mat.supr-conarXiv:cond-mat/9804121

Abstract

The vortex response to various ac-drives has been studied in high quality YBa2Cu4O8 single crystals. Well within the vortex solid phase a re-entrant resistive state has been observed that is characterized by long relaxation times. Pulse current response and IV characteristics reveal that in this state the driven vortex system relaxes in a way to increase t he effective pinning force. A phenomenological model accounts for the observed features, in particular the clock-wise hysteresis of the IV-curves and the increase of the apparent critical current with applied current amplitude.

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