Group seminar at MPQ and Zoom: Collective excitations in a mesoscopic Fermi system

Johannes Reiter, Heidelberg University
Group seminar at MPQ lecture hall and Zoom
Friday, July 14th, 09:00 am (MEZ)

Abstract:

Understanding the emergence of collective behaviour in strongly-interacting mesoscopic systems has been a long-standing challenge in many fields ranging from nuclear to cold atom physics [1,2]. Building on our previously established spilling technique [3] we deterministically prepare few Fermion systems in a tightly confined axisymmetric tweezer and spectroscopically probe the radial quadrupole response of the system across the BEC-BCS crossover. Tuning the interparticle interactions via a broad Feshbach resonance allows us to observe the transition from single-particle to collective excitations. By starting in the few-body limit and deterministically adding particles to our sample we furthermore investigate the emergence of the interaction dependent collective quadrupole mode atom by atom. Finally, we demonstrate the coherence of the former by its excitation and subsequent controlled de-excitation enabling insight  into the breakdown of collectivity.

[1] B. Mottelson Science 193 (4250), 287-294 (1976)
[2] S. Giorgini et al. Rev.Mod.Phys. 80, 125 (2008)
[3] F. Serwane et al. Science 332 (6027), 336-338 (2011)