Stabilization of localized states in dissipative tunneling systems interacting with monochromatic fields

We study the dynamics of an initially localized symmetric two-level system coupled to high-temperature dissipative environments and driven by a strong time-periodic force which corresponds to high-frequency monochromatic light. Qualitative arguments based on the quantized representation of the radiation field predict a wealth of intriguing behaviors which are confirmed and quantified via accurate numerical path integral calculations. With the exception of very strong friction we find that high-frequency driving always helps stabilize localized states, At intermediate friction the delocalization rate approaches a ''universal'' limiting value which is largely independent of the parameters of the environment and of the specifics of the driving force, depending only on its overall strength. This robust behavior implies that localized slates can be stabilized in these systems without much finetuning of external conditions. In the weak friction regime the interplay between phase interference and dissipation results in nonmonotonic Variation of the decay rate with friction and driving frequency. The path integral results are compared to those obtained earlier via analytical treatments. (C) 1997 American Institute of Physics.