Group seminar at MPQ and Zoom: Probing quasiparticle properties in ultracold fermionic gases via Raman transitions

Avishay Grinberg, Physics Department, Technion- Israel Institute of Technology, Hafia, Israel
Group seminar at MPQ lecuture hall and Zoom
Thursday, 27 March, 09:00 am (MEZ)

A gas of ultracold fermionic atoms with tunable interactions serves as an excellent quantum simulator for many fermionic condensed matter systems. In particular, understanding the pairing and condensation of fermions has long been a major goal. A Fermi gas in the BEC-BCS crossover exhibits the highest known T_c/T_F ratio, making it a paradigmatic example of a high-T_c  superfluid. Recently, we developed a unique probing scheme using a two-photon Raman transition. We employ this scheme to reveal the existence and properties of quasiparticles. Additionally, by driving transitions between the two interacting spins, we probe the spin dynamics through the spin-flip correlation function, which is analogous to the Hebel-Slichter (HS) effect observed in superconductors. In superconductors, the HS effect manifests as a peak in relaxation rates, as measured in NMR experiments, and provides key support for Bardeen–Cooper–Schrieffer (BCS) theory. In our experiment, we track the center-of-mass motion following the two-photon transition. Using a Feshbach resonance, we tune the interaction and explore the spin dynamics in the crossover regime. I will present preliminary results showing distinct behavior correlated with T_c and discuss the insights these experiments can provide.