Fermions with tunable interactions... In the Lithium lab we produce binary mixtures of 6Li Fermi gases to investigate fermionic superfluidity across the BEC-BCS crossover. Our main goal is to study two-dimensional fermionic superfluids.

Repulsive Fermi polarons observed in a polarized spin mixture

Landau was first to suggest that collective excitations of particle ensembles could be treated as if they were particles themselves, with properties like momentum and mass. As such, these excitations are known as quasiparticles, and in contrast to free particles they possess a finite lifetime. In this study, we report on the investigation of a particular type of quasiparticle known as a Fermi polaron. This is a quantum impurity that is immersed in a Fermi sea and strongly interacts with it. In particular, Fermi polarons emerging from impurities repelling the surrounding particles are known as repulsive polarons. We could observe well-defined repulsive polarons even at very strong interactions, with impurities possessing the same mass as the surrounding particles. In such a system the existence of long-lived repulsive polarons was thus far debated. For this, we have spectroscopically probed an ultracold Fermi gas of lithium, where atoms in a specific internal spin state acted the role of the impurities interacting with a bath of atoms in another spin state. Our findings offer exciting prospects for studying many-body states that rely on repulsive interactions.

F. Scazza, et al.,
Repulsive Fermi Polarons in a Resonant Mixture of Ultracold 6Li Atoms
Phys. Rev. Lett. 118, 083602 (2017)

Li people

Eleonora Lippi
Master student
Andrea Amico
PhD student
Pedro Tavares
Postdoc
Francesco Scazza
Postdoc
Matteo Zaccanti
Scientific staff
Massimo Inguscio
Scientific staff
Giacomo Roati
Scientific staff
Former members:
Alessia Burchianti
Chiara Fort
Jorge Seman
Giacomo Valtolina

Li contacts

For further information, request of material, job opportunities, please contact:

Giacomo Roati
(roati@lens.unifi.it)

Li funding