Regensburg 2002 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 5: Quantenpunkte und -dr
ähte: Transporteigensch. I
HL 5.1: Vortrag
Montag, 11. März 2002, 10:30–10:45, H17
Dynamics of a large-spin-boson system — •T. Vorrath1, T. Brandes2, and B. Kramer1 — 1I. Institut für Theoretische Physik, Jungiusstr. 9, 20355 Hamburg — 2Dept. of Physics, UMIST, PO Box 88, Manchester M60 1QD, UK
A double quantum dot interacting with photons or phonons can be regarded – in certain regimes of parameters – as a biased two level system coupled to a bosonic bath [1]. This is a realization of the spin-boson-model [2]. We consider a system of several double quantum dots coupled to each other via a common bosonic environment. We use a large-spin boson model to investigate collective effects of this system in which the large pseudo-spin represents the double quantum dots. An equation for the time evolution of the z-component <Jz> of the large pseudo-spin, i.e. the collective inversion, is derived from a generalized master equation for weak and for strong coupling to the bosonic bath. In the strong coupling limit, a polaron transformation is applied to account for arbitrarily high couplings. The environment is modeled by an ohmic bath at temperature T=0. We find that for large times <Jz> relaxes extremely slowly towards a highly correlated ground state with maximum value ± J [3]. The results are compared with those obtained for the weak coupling limit, where the interaction with the environment is taken into consideration by perturbation theory.
[1] T. Brandes and B. Kramer, Phys. Rev. Lett. 83, 3021 (1999).
[2] A. Leggett et al., Rev. Mod. Phys. 59, 1 (1987).
[3] T. Vorrath, T. Brandes and B. Kramer, to be published in Proc. of MB11 (2001).