# Berlin 2014 – wissenschaftliches Programm

## Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

# Q: Fachverband Quantenoptik und Photonik

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

### Q 32.6: Poster

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

**Bose-Einstein Condensate in Gravitational Cavity: Comparing Soft and Hard Wall Boundary Condition** — •Javed Akram^{1} and Axel Pelster^{2} — ^{1}Department of Physics, Freie Universität Berlin, Germany — ^{2}Fachbereich Physik und Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, Germany

Within a one-dimensional gravitational cavity the effect of gravity is compensated by an exponentially decaying potential, which is created by the total internal reflection of an incident laser beam from the surface of a dielectric serving as a mirror for the atoms. We describe a weakly interacting Bose-Einstein condensates (BEC) in such a one-dimensional gravitational cavity with different trial mean-field condensate wave functions, where both its width and its height are considered as variational parameters. In particular, we determine the variational results for the BEC equilibrium configuration when the surface is modelled by a soft or a hard wall boundary condition. By considering small deflections around the respective equilibrium positions, we also investigate the collective excitations of the BEC. Furthermore, we analyze how the BEC cloud expands ballistically due to gravity after switching off the evanescent laser field.