Erlangen 2018 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 51: Poster: Quantum Optics and Photonics IV
Q 51.14: Poster
Mittwoch, 7. März 2018, 16:15–18:15, Redoutensaal
Persistent oscillations in the Higgs mode in a cigar-shaped ultracold Fermi gas — •Simon Hannibal1, Peter Kettmann1, Mihail Croitoru2, Vollrath Martin Axt2, and Tilmann Kuhn1 — 1Institute of Solid State Theory, University of Münster — 2Theoretical Physics III, University of Bayreuth
Ultracold Fermi gases in optical traps provide a unique system to study the many body physics of systems composed of fermionic constituents. Both, the BEC and the BCS superfluid state are observed. Furthermore, the transition between these states is well controllable by means of a Feshbach resonance, which allows to tune the scattering length over a wide range from negative to positive values.
We employ an inhomogeneous BCS mean field theory and calculate the dynamics of the BCS gap of a confined ultracold Fermi gas after an interaction quench. Due to the spontaneously broken U(1) symmetry in the superfluid phase two fundamental modes of the BCS gap evolve, i.e., the amplitude (Higgs) and phase (Goldstone) mode. Here, we focus on the Higgs mode on the BCS side of the BCS-BEC crossover.
We investigate the dynamics resulting from interaction quenches starting deep in the BCS regime and ending in the BCS-BEC crossover region. We find a nonlinear persistent dynamics with one dominant frequency. For all quenches, this frequency stays closely connected to the long time average of the modulus of the BCS gap. We show that both are determined by a breaking of Cooper pairs at the time of the quench. Furthermore, we find that our model exhibits a chaotic behavior for large quenches ending in the BCS-BEC crossover region.