On May 27, Hauke Biss, Universität Hamburg, Germany, and colleagues sat down with the Physical Review Journal Club to discuss the recently published Physical Review Letters paper “Excitation Spectrum and Superfluid Gap of an Ultracold Fermi Gas.” Biss and colleagues utilized Bragg spectroscopy to measure the full momentum-resolved low-energy excitation spectrum of strongly interacting ultracold Fermi gases.
This technique enabled the team to directly observe the smooth transformation from a bosonic to a fermionic superfluid that takes place in the BEC-BCS crossover. The team also used spectra to determine the evolution of the superfluid gap and find excellent agreement with previous experiments and self-consistent T-matrix calculations both in the BEC and crossover regime. However, toward the BCS regime a calculation that includes the effects of particle-hole correlations shows better agreement with the presented data. The research was summarized in Physics Magazine.
Biss presented the team’s data, then joined collaborators to answer all participant questions in a live question-and-answer session moderated by Zoran Hadzibabic, Cavendish Laboratory, University of Cambridge, UK.