Tunneling and resonant tunneling of fluxons in a long Josephson junction

We study fluxon tunneling both across one microshort-type barrier and resonant tunneling across two barriers. We have derived an effective Hamiltonian (using the inverse scattering transform) to study the effect of plasmons on the tunneling. Using a specially derived perturbation scheme, we found two effects: (1) Emission of plasmons and, hence, suppression of quantum effects. Due to the gap in the plasmon spectrum, this is an exponentially small effect. (2) Virtual processes involving plasmons close-quote emission and absorption cause an enhancement of the tunneling probability. The magnitude of this enhancement is not exponentially small. We conclude that macroscopic quantum tunneling of fluxons can be observed. We further predict that fluxons close-quote resonant tunneling across two barriers can also be observed. This phenomenon provides an ideal test for the quantum behavior of the fluxons. copyright 1997 The American Physical Society