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A: Fachverband Atomphysik
A 10: Bose-Einstein Condensation (joint session A/Q)
A 10.1: Vortrag
Montag, 5. März 2018, 14:00–14:15, K 2.016
Nonequilibrium Quantum Phase Transition in a Hybrid Atom-Optomechanical System — •Niklas Mann1, M. Reza Bakhtiari1, Axel Pelster2, and Michael Thorwart1 — 1I. Institut für Theoretische Physik, Universität Hamburg, Jungiusstraße 9, 20355 Hamburg, Germany — 2Physics Department and Research Center OPTIMAS, Technical University of Kaiserslautern, Erwin-Schrödinger Straße 46, 67663 Kaiserslautern, Germany
We consider a hybrid quantum many-body system formed by both a vibrational mode of a nanomembrane, which interacts optomechanically with light in a cavity, and an ultracold atom gas in the optical lattice of the out-coupled light. After integrating over the light field, an effective Hamiltonian reveals a competition between the localizing potential force and the membrane displacement force. For increasing atom-membrane interaction we find a nonequilibrium quantum phase transition from a localized non-motional phase of the atom cloud to a phase of collective motion. Near the quantum critical point, the energy of the lowest collective excitation vanishes, while the order parameter of the condensate becomes non-zero in the symmetry-broken state. The effect occurs when the atoms and the membrane are non-resonantly coupled.