Münster 1997 – wissenschaftliches Programm
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CP: Chemische Physik
CP 16: Poster zur Sitzung CP6
CP 16.6: Poster
Dienstag, 18. März 1997, 18:30–21:15, FBH
Quantum mechanical and quasi-classical dynamics of coupled spin-boson systems — •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 quasiparticle coupled to polarization vibrations in a dimer. This model (harmonic oscillator coupled to a two-level system) is interesting in various other physical situations, e.g. the spin-1/2 case of the Jaynes-Cummings model. We found that a complementary approach to the usual quasi-classical treatment of the spin-boson model may be more suitable for the spin-1/2 case.
The spectra of the eigenvalues of the system show a quite regular behaviour especially in the strong coupling range where the usual quasi-classical dynamical treatment predicts chaotic behaviour. The integrable part of the total Hamiltonian, responsible for the regular behaviour, can be diagonalized by a unitary transformation allowing us to give approximate analytic expressions for the eigenvalues for intermediate and for strong coupling. Starting the quasi-classical description from the transformed Hamiltonian, we found that the system is nearly integrable in contrast to the pronounced chaotic behaviour of the usual quasi-classical description, especially in the strong coupling limit. Considering the time evolution in the transformed system, we can identify initial conditions where a quasi-classical description works well at least for short times.