Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 27: Phase Transitions

Q 27.5: Talk

Wednesday, March 13, 2024, 12:15–12:30, Aula

Nanomechanically-induced quantum phase transition to a self-organized density-wave BEC — •Milan Radonjić^1,2, Leon Mixa¹, Axel Pelster³, and Michael Thorwart¹ — ¹I. Institute of Theoretical Physics, University of Hamburg, Germany — ²Institute of Physics Belgrade, University of Belgrade, Serbia — ³Physics Department and Research Center OPTIMAS, University Kaiserslautern-Landau, Germany

We study nonequilibrium quantum phase transition (NQPT) in a hybrid quantum many-body system consisting of a vibrational mode of a nanomembrane interacting optomechanically with a cavity, whose output light couples to two internal states of an ultracold Bose gas held in an external quasi-1D box potential. For small effective membrane-atom couplings, the system is in a homogeneous BEC ground state, with no membrane displacement. Depending on the transition frequency between the two internal atomic states, either one or both internal states are occupied. By tuning the two couplings outside the respective critical regions, the system transitions to a symmetry-broken self-organized BEC phase, which is characterized by a sizeably displaced membrane and density-wave-like BEC profiles. This NQPT is both discontinuous and continuous for a certain interval of transition frequencies, and purely discontinuous outside of it.

Keywords: hybrid quantum system; nonequilibrium quantum phase transition; optomechanics; internal state coupling