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Quantum Creep in Y1-xPrxBa2Cu3O7$ Crystals: Magnetic Relaxation and Transport

T. Stein, G. A. Levin, C. C. Almasan, D. A. Gajewski, M. B. Maple

cond-mat.supr-conarXiv:cond-mat/9902076

Abstract

We report transport and magnetic relaxation measurements in the mixed state of strongly underdoped Y1-xPrxBa2Cu3O7 crystals. A transition from thermally activated flux creep to temperature independent quantum flux creep is observed in both transport and magnetic relaxation at temperatures T * 5 K. Flux transformer measurements indicate that the crossover to quantum creep is preceded by a coupling transition. Based on these observations we argue that below the coupling transition the current is confined within a very narrow layer beneath the current contacts.

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