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Enhanced Macroscopic Quantum Tunneling in Bi2Sr2CaCu2O8+δ Intrinsic Josephson Junction Stacks

X. Y. Jin, J. Lisenfeld, Y. Koval, A. Lukashenko, A. V. Ustinov, P. Müller

cond-mat.supr-conarXiv:cond-mat/0603445

Abstract

We have investigated macroscopic quantum tunneling in Bi2Sr2CaCu2O8+δ intrinsic Josephson junctions at millikelvin temperatures using microwave irradiation. Measurements show that the escape rate for uniformly switching stacks of N junctions is about N2 times higher than that of a single junction having the same plasma frequency. We argue that this gigantic enhancement of macroscopic quantum tunneling rate in stacks is boosted by current fluctuations which occur in the series array of junctions loaded by the impedance of the environment.

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