Bonn 2025 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 50: Ultracold Matter (Fermions) I (joint session Q/A)
Q 50.5: Talk
Thursday, March 13, 2025, 12:00–12:15, HS V
Fate of the Higgs mode in confined fermionic superfluids — •René Henke1, Cesar R. Cabrera1, Hauke Biss1, Lukas Broers2, Jim Skulte2, Hector Pablo Ojeda Collado2, Ludwig Mathey1,2, and Henning Moritz1 — 1Institut für Quantenphysik, Universität Hamburg — 2Zentrum für optische Quantentechnologien, Universität Hamburg
In superconductors and superfluids, the order parameter characterizes the phase coherence and collective behavior of the system. Fluctuations in the phase and amplitude of the order parameter give rise to the Goldstone and Higgs modes, respectively. In confined systems, these dynamics as well as the static properties of superfluids are expected to change dramatically. As an example of the latter, shape resonances in nano wires and films are predicted to enhance the superfluid gap and raise Tc.
Here, I will report on the observation of a hybridization between Higgs and breathing oscillations in a quasi-2D fermionic superfluid. When modulating the confinement, we observe a well-defined collective mode throughout the BEC-BCS crossover. In the BCS regime, the excitation energy follows twice the pairing gap, as expected for an amplitude oscillation, drops below it in the strongly correlated regime, and approaches the breathing mode frequency, in excellent agreement with an effective field theory for order parameter dynamics. The mode vanishes when approaching the superfluid critical temperature. Our results provide insights into the complex interplay between confinement-induced effects and fundamental excitations in reduced dimensions.
Keywords: ultracold Fermi gases; superfluids; low dimensional systems; Higgs mode