SAMOP 2023 – wissenschaftliches Programm

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Q: Fachverband Quantenoptik und Photonik

Q 22: Poster II

Q 22.4: Poster

Dienstag, 7. März 2023, 16:30–19:00, Empore Lichthof

Non-equilibrium steady states of driven dissipative quantum gases beyond ultraweak coupling — •Adrian Köhler, André Eckardt, and Alexander Schnell — TU Berlin, Berlin, Deutschland

The microscopic description of ideal quantum gases in presence of a finite coupling to a heat bath poses a theoretical challenge. Even though the system itself is non-interacting, the system-bath coupling is cubic in the field operators making the problem interacting. As a first step, we study the mean-field dynamics of the single-particle density matrix under the Redfield quantum master equation. We find that typical steady-state solvers converge only in a very limited parameter regime, forcing one to rely on numerically more costly time-integration. We also discuss approaches to overcome this problem using perturbation theory in the coupling strength. We apply our approach to a Bose gas coupled to two baths of different temperature, for which in the regime of ultraweak coupling Bose condensation is predicted also in cases, where both bath temperatures lie well above the equilibrium crtitical temperature [PRL 119, 140602]. In the regime of finite coupling, we find that steady-state solutions of the Redfield quantum master equation form a condensate in the ground state.