Erlangen 2022 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 8: Quantum Gases (Bosons) II

Q 8.4: Talk

Monday, March 14, 2022, 17:15–17:30, Q-H10

Experimental characterization of a dissipative phase transition in a multi-mode system — •Marvin Röhrle, Jens Benary, Christian Baals, Erik Bernhart, Jian Jiang, and Herwig Ott — Department of Physics and Research Center OPTIMAS, Erwin-Schrödinger-Straße 46, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany

We experimentally investigate the behavior of a driven-dissipative Bose-Einstein condensate of weakly interacting ⁸⁷Rb atoms in a 1-D optical lattice. The dissipation is induced by a scanning electron microscope setup, which allows us to observe a single site time resolved. Tunneling from the neighboring sites makes up the driving force.

By changing the tunnel coupling J of the lattice, a dissipative phase transition from a coherent super fluid phase to an incoherent phase can be seen. In the vicinity of the phase transition, both branches coexist in a meta stable region depending on the initial state. Measuring the relaxation rates between the two states allows us to approximate the adiabatic decay rate and find the critical point. In every individual realization of the experiment, the filling of the site shows a digital behavior, which is visible as pronounced jumps in the site occupation. We find that the switching between both states takes only a few tunneling times despite hundreds of atoms tunneling. Furthermore, starting from an initially filled site, the losses induce a super fluid current which keeps the site filled. This complete extinction of a matter wave within a medium indicates the onset of coherent perfect absorption.