Comunicazione

Probing the spectral response of ultracold Fermi gases after quench to strong repulsive interactions.

Amico A., Scazza F., Tavares P., Valtolina G., Inguscio M., Zaccanti M., Roati G.
  Lunedì 11/09   14:30 - 18:30   Aula A224   II - Fisica della materia
We will present our recent investigations on ultracold Fermi gases with strong repulsive interactions employing reverse radio-frequency spectroscopy. In a first experiment, we focus on spin-imbalanced mixtures in the regime of strong repulsive interactions. We observe well-defined coherent quasiparticles (polaron) even for unitarity-limited interactions. In particular we find that above a critical value of repulsion, the polaron energy exceeds the Fermi energy of the bath while its effective mass diverges and even turns negative. In a second ongoing experiment we investigate the opposite limit of balanced Fermi mixtures. We use rapid radio-frequency transfers to quench repulsive interactions on a timescale comparable with the Fermi time. We probe the spectral response of the many-body system investigating both the growth of magnetic spin-correlation in the repulsive gas and the decay processes into a paired state or into an attractive polaron.