Erlangen 2018 – wissenschaftliches Programm
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Q: Fachverband Quantenoptik und Photonik
Q 51: Poster: Quantum Optics and Photonics IV
Q 51.13: Poster
Mittwoch, 7. März 2018, 16:15–18:15, Redoutensaal
Observation of a pure Goldstone mode in the quench dynamics of an ultracold BCS Fermi gas — •Peter Kettmann1, Simon Hannibal1, 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 are a convenient system to probe and study the properties of phases like the BEC and the BCS phase and the crossover in between those regimes. In particular, ultracold Fermi gases can be used as a test bed to study the two fundamental dynamical modes –the Higgs and the Goldstone mode– which result from spontaneous symmetry breaking in these phases.
We investigate the Goldstone mode in the dynamics of a cigar-shaped cloud of ultracold 6Li after a moderate interaction quench on the BCS side of the BCS-BEC crossover. To this end, we numerically solve Heisenberg’s equations of motion for the Bogoliubov single-particle excitations in the framework of the Bogoliubov-de Gennes formalism. We observe that the quench leads to the emergence of a homogeneous Goldstone mode which does not couple to the trap and which is –as a result– gapless. In contrast to previous studies, we therefore observe the emergence of a pure Goldstone mode, i.e., a Goldstone mode in the original sense of the Goldstone theorem.
Furthermore, we investigate several ways to experimentally access the pure Goldstone mode, i.e., via a collective motion of the condensate, via its single-particle excitations, and via an interference setup.