Quantum tunneling of semifluxons in a 0-π-0 long Josephson junction -: art. no. 054527

We consider a system of two semifluxons of opposite polarity in a 0-pi-0 long Josephson junction, which classically can be in one of two degenerate states: up arrow down arrow or down arrow up arrow. When the distance a between the 0-pi boundaries (semifluxon's centers) is a bit larger than the crossover distance a(c), the system can switch from one state to the other due to thermal fluctuations or quantum tunneling. We map this problem to the dynamics of a single particle in a double well potential and estimate parameters for which quantum effects emerge. We also determine the classical-to-quantum crossover temperature as well as the tunneling rate (energy level splitting) between the states up arrow down arrow and down arrow up arrow.