Quantum Kicked Rotor Studies in the BEC-BCS Crossover

The interacting quantum kicked rotor (QKR) is an outwardly simple model for quantum chaos that has applications in interferometry and transport [1,2,3,4]. We utilize tunable interactions in fermionic lithium-6 to prepare ultracold samples of pairs throughout the BEC-BCS crossover. We explore how energy vs. kick period QKR spectra change with scattering length and temperature, and with the formation of pairs. The energy spectra show resonances and anti-resonances which can remain as we increase interaction strength. At the same time, our results indicate that strong interactions can still lead to sizable changes to the spectral structure, including shifts in the shape and location of the anti/resonances related to the interaction strength and sign. On the BEC side, we observe a suppression of the main atomic resonance in favor of the main molecular resonance as temperature is reduced below the pair binding temperature. At our coldest temperatures, increasing interactions leads to a suppression of the main molecular resonance and rise in the background, pointing to interaction-induced dephasing. At the unitarity limit and BCS side, the main spectral peaks survive and display new substructures requiring further exploration.