Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 1: Hauptvortrag Brandes

HL 1.1: Hauptvortrag

Montag, 24. März 2003, 09:30–10:15, POT/81

Electron-Phonon Cavities — •Tobias Brandes — Dept. of Physics, UMIST, Manchester M60 1QD (UK)

Coulomb interactions between electrons in coupled quantum dots can be exploited to define very small effective Hilbert spaces that allow to study, e.g., the controlled time-evolution of quantum superpositions. Interactions with bosonic degrees of freedom (photons, phonons) usually lead to decoherence that can be modified in cavities, in analogy with cavity QED. In fact, electron transport experiments in nano-electromechanical systems (individual molecules, free-standing semiconductor dots) reveal phonon confinement signatures and indicate that vibrational degrees of freedom are more than just a mere source of dissipation.

We review some recent theoretical results, starting with a phonon cavity model that predicts a reduced charge dephasing during time-dependent double quantum dot ‘gate’ operations, and resonances that are related to a recently observed single electron recoil effect. We then discuss models describing the interaction of a single cavity boson mode with electrons, the simplest of which are an ‘electron transport’ version of the Rabi Hamiltonian and a quantum dynamical delta barrier scatterer. Large-spin-boson models are then discussed in the context of collective effects with possible realisations in quantum dots arrays, nano-magnets or exciton-polaritons. In the single-boson mode case, the model shows interesting features of quantum chaos as triggered by precursors of a quantum phase transition.