Theoretical studies on Josephson pi states

The Josephson effect under particle-number restriction is investigated base d on the Feynman two-state model. The existence of new dynamical states of the Josephson phase inherent in such a restricted situation is shown. The n ew state describes a number of features recently observed in a superfluid H e-3 weak-link system. Quantum decay from Josephson pi states is also invest igated. Since the pi state has two different decay paths, they can interfer e during the decay processes by quantum tunneling due to a topological phas e originating from total particle-number restriction, and result in a parit y effect for tunneling. (C) 1999 Academic Press.