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Quantum Effects in Resistance-Shunted Josephson Junctions

Takeo Kato, Masatoshi Imada

cond-mat.supr-conarXiv:cond-mat/9908192

Abstract

Thermodynamics and transport properties of resistance-shunted Josephson junctions are studied theoretically in the tight-binding limit EC/EJ<<1, where EC and EJ are a charging energy and a Josephson coupling energy respectively. Based on a phenomenological harmonic-oscillator model, weak coupling region K=RQ/R<<1 is analytically studied, where R and RQ=h/(2e)2 are a shunted resistance and the quantum resistance. In addition to the effective bandwidth, we find that this multi-level system genuinely has a novel crossover at lower energy below which the density of states becomes strongly degenerate. These two energy scales control the linear DC responses, optical responses, and nonlinear I-V characteristics. The lower energy crossover indicates the existence of a new class of strongly-correlated phenomena beyond the framework of the Kondo problem.

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