Regensburg 1998 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 18: POSTER I
DY 18.36: Poster
Montag, 23. März 1998, 14:30–17:30, D
Dynamics of coupled spin-boson systems: Quantum mechanical and quasi-classical treatment — •R. Steib1, P. Reineker1, J. L. Schoendorff2, and H. J. Korsch2 — 1Abteilung Theoretische Physik, Universität Ulm, 89069 Ulm — 2Fachbereich Physik, Universität Kaiserslautern, 67653 Kaiserslautern
We investigate a system described by a harmonic oscillator coupled to a two-level system. This model is interesting for various physical situations, e.g. the transport of excitons in dimers or the spin-1/2 case of the Jaynes-Cummings model.
We use an approach complementary to the usual quasi-classical treatment. Identifying an integrable Hamiltonian in the strong coupling case, we find that, especially in the strong coupling limit, the system is nearly integrable in contrast to the pronounced chaotic behavior of the usual quasi-classical description. Although both Hamiltonians considered are equivalent (related by an unitary transformation), the resulting quasi-classical equations lead to a qualitatively different (chaotic/regular) behavior.
Thus the transition from the quantum description to the quasi-classical approximation depends on the selection of a suitable reference Hamiltonian. Considering the quasi-classical treatment using the transformed Hamiltonian we can identify quantum initial states where a quasi-classical approximation is reasonable. Furthermore we find trapped states even in the quantum mechanical treatment.