Non-standard Bose condensation in non-equilibrium steady states of driven-dissipative systems

André Eckardt, Max-Planck-Institute für Physik komplexer Systeme, Dresden

22.01.2018 at 10:15 

I will talk about Bose condensation (as a paradigmatic example ordering) in non -equilibrium steady states of driven-dissipative Bose gases, considering three basic scenarios: periodically forced (Floquet) systems coupled to a heat bath [1], systems coupled to two heat baths of different temperature [2], and pumped lossy photonic systems interacting with a heat bath [3]. Unlike equilibrium states, which are determined completely by a few thermodynamic variables like the bath temperature only, non-equilibrium steady states obey less restrictions and depend sensitively on the very details of the environment. This offers great freedom to tailor the properties of a quantum system by engineering its environment.
We show that this freedom can be used for the robust preparation of excited -state and fragmented Bose  condensates[1,3]. This is explained by an analytical theory describing also transitions between states with condensates in different modes. It describes experimental results for photons and exciton-polaritons in microcavities [3]. I will also present an example that shows that Bose condensation can be induced by coupling a system to two competing baths, both of which have temperatures orders of magnitude above the equilibrium critical temperature [2]. This effect relies on a suppression of long-wavelength modes as a result of the competition between both baths. Finally, I will discuss recent results regarding the treatment of finite-temperature baths in interacting systems.

Based on references:
[1] D. Vorberg et al., PRL 111, 240405 (2013) & PRE 92, 062119 (2015)
[2] A. Schnell et al., PRL 119, 140602 (2017)
[3] A. Leymann et al., PRX 7, 021045 (2017); D. Vorberg, R. Ketzmerick, A. Eckardt, in preparation