Dissipative tunneling in asymmetric double-quantum-well system. A coherence phenomenon

Recent experiments on asymmetric double-quantum-well systems revealed unexpected long time scales of resonant tunnel processes as well as deviations from the expected dependence of the tunneling lifetime T on the barrier thickness. Both effects are related to the presence of dissipative processes. Starting from microscopic expressions for T beyond the usual golden rule approach we show that the observed behavior is a consequence of Fano interference, which implies that low-temperature dissipative tunneling can be treated as a totally coherent process. Including disorder due to interface roughness, these Fano interferences lead to a nonexponential and slowed-down decay.