# Berlin 2014 – wissenschaftliches Programm

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# Q: Fachverband Quantenoptik und Photonik

## Q 32: Poster: Quantum gases, ultracold atoms and molecules

### Q 32.25: Poster

### Mittwoch, 19. März 2014, 16:30–18:30, Spree-Palais

**Non-equilibrium polaron physics of ultra cold bosonic lattice gases** — •Fabian Grusdt^{1,2}, Aditya Shashi^{2}, Dmitry Abanin^{2,3}, and Eugene Demler^{2} — ^{1}Department of physics, research center OPTIMAS and graduate school MAINZ, TU Kaiserslautern — ^{2}Physics Department, Harvard University — ^{3}Perimeter Institute, Waterloo, Canada

We discuss a single impurity in a one-dimensional optical lattice immersed in a homogeneous three dimensional superfluid Bose Einstein condensate. Interactions with the phonon modes of the latter lead to the formation of a stable quasi particle, the polaron. We investigate the static and dynamic properties of the polaron using a variational mean-field treatment. We consider the effect of an external driving force which drives subsonic Bloch oscillations of the polaron. In the weak coupling limit the polaron adiabatically follows its ground state and a detection of the polaron trajectory in real space can be used for a direct measurement of the renormalized polaron dispersion relation. We show that for stronger coupling the polaron trajectory is superimposed by a constant drift velocity, accompanied by polaron diffusion as well as phonon emission. We report on subtle deviations of the current- force relation from the standard Esaki-Tsu type expression and show that they can be explained by introducing an internal polaron structure.