Theory of superconductor-insulator transition in single Josephson junctions

A nonband theory is developed to describe the superconductor-insulator transtition in resistively shunted, single Josephson junctions. The I-V characteristic is formulated by a Landauer-like formula and evaluated by the path-integral transfer-matrix method. The result is consistent with the recent experiments at around 80 mK. However, the insulator phase shrinks with decreasing temperature indicating that the single Josephson junction becomes all superconducting at absolute zero temperature, as long as dissipation is present.