Düsseldorf 2007 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 40: Quantengase (Spinor-Gase)

Q 40.5: Talk

Wednesday, March 21, 2007, 15:00–15:15, 6J

Manifestation of dynamical screening in a spinor condensate — •Navez Patrick — Labo Vaste-Stoffysica en Magnetisme, Katholieke Universiteit Leuven, Celestijnlaan 200 D, B-3001, Heverlee, Belgium — Fachbereich Physik, Universitaet Duisburg-Essen, Lotharstrasse 1, 47048 Duisburg, Germany

The Landau criterion is a necessary but not sufficient condition for the occurrence of superfluidity. In particular, it ignores that the normal fluid consists of thermal excitations, some of them with a group velocity higher than the critical one. As a consequence, thermal atoms prevent dissipationless motion by colliding with the superfluid ones, unless a mechanism forbids this process. A possible mechanism is the dynamical screening of the interaction force between the thermal atoms and the superfluid ones. A local modification of the amplitude of the superfluid macroscopic wavefunction would induce a local diminution of the potential energy resulting, under some conditions, in a total screening of this interaction force. We propose an experimental setup in which the measurement of the dynamic structure factor in a spinor Bose gas could allow the visualization of this screening phenomenon.

P. Navez, Physica A 356, 241 (2005); P. Navez and R. Graham, Phys. Rev. A 73, 043612 (2006).