Macroscopic Quantum Tunneling of a Fluxon in a Long Josephson Junction

概要

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Macroscopic quantum tunneling (IVIQT) for a single fluxon nnoving along a long Josephson junc-tion is studied theoretically. To introduce a fluxon-pinning force, we consider inhomogeneitiesmade by modifying thickness of an insulating layer locally. Two different situations are stvndied:one is the quantunu tunneling from a metastable state caused by a single inhomogeneity, andthe other is the quantum tunneling in a two-state system nnade by two inhomogeneities. In thequanttrrn tunneling from a metastable state, the decay rate is estimated within the WKB approx-iunation. Dissipation effects on a fltxxon dynamics are taken into account by the Caldeira-Leggetttheory. We propose a device to observe quantttun tunneling of a fluxon experimentally. Requiredexperimental resolutions to observe IVIQT of a fluxon seem attainable within the presently avail-able micro-fabrication technique. For the two-state system, we study quantum resonance betxveentwo stable states, i.e., macroscopic quantunu coherence (MQC), From the estimate for dissipationcoefficients due to quasiparticle tvtnneling, the observation of MQC appears to be possible withinthe Caldeira-Leggett theory.
社団法人日本物理学会の論文
1996-09-15