D. M. Kennes, O. Kashuba, M. Pletyukhov, H. Schoeller, V. Meden
We study the nonequilibrium dynamics of the unbiased, ohmic spin-boson model close to the coherent-to-incoherent transition. In a first setup the system is prepared in a product state. Using complementary renormalization group methods we obtain numerical results for the spin expectation value on all time scales. They are supplemented by an analytical study for intermediate times. In the coherent regime the time evolution for those is characterized by the subtle interplay of damped oscillatory and purely exponential terms. Secondly, we investigate the dynamics when abruptly switching the coupling from a value in the incoherent regime to one in the coherent one. The incoherent dynamics before the quench heavily affects the one after it up to the extent that a critical coupling strength is required to observe nonmonotonic behavior. This exemplifies the importance of non-markovian memory.
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http://arxiv.org/abs/1211.0293
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