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 H amiltonian (using the inverse scattering transform) to study the effec t of plasmons on the tunneling. Using a specially derived perturbation scheme, we found two effects:, (1) Emission of plasmons and, hence, s uppression of quantum effects. Due to the gap in the plasmon spectrum, this is an exponentially small effect. (2) Virtual processes involvin g plasmons' emission and absorption cause an enhancement of the tunnel ing probability. The magnitude of this enhancement is not exponentiall y small. We conclude that macroscopic quantum tunneling of fluxons can be observed. We further predict that fluxons' resonant tunneling acro ss two barriers can also be observed. This phenomenon provides an idea l test for the quantum behavior of the fluxons.