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 shunt resistance and the quantum resistance. In addition to an effective bandwidth 2ℏΔeff, we find that this multi-level system genuinely has a novel crossover at lower energy KℏΔeff 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.
- Coulomb blockade
- Josephson junctions
- Macroscopic quantum effects
- Superconductor-insulator transition
ASJC Scopus subject areas
- General Physics and Astronomy