Berlin 2014 – wissenschaftliches Programm
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A: Fachverband Atomphysik
A 34: Poster: Ultra-cold atoms, ions and BEC (with Q)
A 34.26: Poster
Mittwoch, 19. März 2014, 16:30–18:30, Spree-Palais
Nonequilibrium BCS Dynamics of Ultracold Fermi Gases — •Peter Kettmann1, Simon Hannibal1, Mihail Croitoru2, Alexei Vagov3, Vollrath Martin Axt3, and Tilmann Kuhn1 — 1Institute of Solid State Theory, University of Münster — 2Condensed Matter Theory, University of Antwerp — 3Theoretical Physics III, University of Bayreuth
Ultracold Fermi gases are a convenient testbed for complex interacting Fermi systems like, e.g., superconductors. They are on the one hand easily accessible in experiment. On the other hand their interparticle interaction strength can be tuned to pass from a BCS to a BEC state. In this way, many-body effects in strongly correlated Fermi systems like high-Tc superconductors can be tested in a controlled way.
We investigate the BCS phase of an ultracold Fermi gas. In particular we calculate the nonequilibrium dynamics of a confined 6Li gas after a sudden excitation, which can be achieved, e.g., by an abrupt change of an external magnetic field or the system confinement. We show that the dynamics of the BCS gap is given by a collective damped oscillation breaking down after a certain time. Afterwards a rather chaotic oscillation appears. We explain this behavior by expressing the quasiparticle equations of motion in terms of a set of coupled oscillators.
Studying systems with different parameters we see that the dynamics show a more or less pronounced initial part of the oscillation depending on the confinement. This is related to size-dependend superfluid resonances predicted by recent theoretical studies [1] and thus to the BCS-BEC crossover. [1] A. A. Shanenko et al., PRA 86, 033612 (2012)