, Volume 116, Issue 1-2, pp 21-60

Phase Diffusion and Suppression of the Supercurrent by Quantum-Mechanical Fluctuations of the Josephson Plasma at Small Superconducting Point Contacts

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Abstract

The RCSJ model of resistively and capacitively shunted Josephson junctions is used to describe superconducting point contacts over a wide range of resistances up to the metallic–tunneling transition. Their small dynamic capacitance of order C = 0.1 fF due to the point-contact geometry results in a huge plasma frequency. The critical current is then strongly suppressed and the contact resistance becomes finite because of quantum-mechanical zero-point fluctuations of the Josephson plasma and the rather large escape rate out of the zero-voltage state due to quantum tunneling. We test the predictions of the RCSJ model on the classical superconductors lead, indium, aluminum, and cadmium.