Fermions with tunable interactions... In the lithium lab we produce ultracold Fermi gases of 6Li to explore out-of-equilibrium dynamics and transport phenomena in strongly correlated fermionic matter. Atoms are confined into light-imprinted potential structures, simulating the motion of electrons in solid state devices. Our main goal is the study of two-dimensional strongly correlated phases, such as superfluidity across the BCS-BEC crossover and its robustness to disorder.

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

Giulia Del Pace
PhD student
Woo Jin Kwon
Postdoctoral fellow
Francesco Scazza
Scientific staff
Matteo Zaccanti
Scientific staff
Massimo Inguscio
Scientific staff
Giacomo Roati
Scientific staff
Former members:
Andrea Amico
Alessia Burchianti
Chiara Fort
Riccardo Panza
Jorge Seman
Pedro Tavares
Giacomo Valtolina

Li contacts

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

Giacomo Roati
(roati@lens.unifi.it)

Li funding

ERC CoG QUFERM2D
EU Quantum Flagship
Qombs (2018-2021)
PRIN 2017 CEnTraL
Progetto Ente Cassa QuSiM2D
H2020-MSCA-IF-2018 VorDIST
H2020-MSCA-IF-2015 SCOUTFermi2D