Dissipative Phase Transition in a Mesoscopic Josephson Junction in a Weak Magnetic Field

A dissipative phase transition (DPT) is found in resistively shunted (4–75kΩ) mesoscopic Josephson junctions owing to suppression of macroscopic quantum tunneling of phase by the interaction with dissipative quantum-mechanical environment. We have studied the behavior of this transition as a function of magnetic field. Instead of a field-induced insulator-superconductor transition, we find a hysteretic insulator–insulator (I–I) transition. The phase diagram for the DPT in a weak magnetic field is outlined.