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.

Witnessing ultracold fermions correlate in real time

Strong interactions among fermionic particles in condensed matter are known to foster rich phase diagrams, where distinct microscopic mechanisms compete with one another. In this work, we reveal the emergence of two competing instabilities in a paradigmatic model system, i.e., a Fermi gas of ultracold atoms. While it has been established that a cold gas of atoms subject to strong interactions is unstable towards forming pairs of oppositely oriented spins, a long-standing issue is whether strong repulsion can trigger fermions to build up correlations and develop ferromagnetic order. Here, we probe the out-of-equilibrium dynamics of a repulsive Fermi gas with unprecedented time resolution, exploiting a pump-probe spectroscopic technique akin to the ultrafast spectroscopy used in the solid state. In this way, we witness the real-time growth of spin anti-correlations in the gas driven only by repulsive interactions. Their interplay with the tendency of fermions to pair up is found to persist over long time scales, giving rise to a novel, emulsion-like metastable state unforeseen thus far. These findings represent an important testbed for current and future theories, while they also afford exciting perspectives for accessing elusive regimes of fermionic superfluidity.

A. Amico, F. Scazza, G. Valtolina, P. E. S. Tavares, W. Ketterle, M. Inguscio, G. Roati, and M. Zaccanti
Time-Resolved Observation of Competing Attractive and Repulsive Short-Range Correlations in Strongly Interacting Fermi Gases
Phys. Rev. Lett. 121, 253602 (2018)

See also the Physics Viewpoint by L. LeBlanc:

L. LeBlanc
The Quest to Make a Ferromagnet with Cold Atoms
Physics 11, 131 (2018)

Li people

Alessandro Muzi Falconi
Master student
Giulia Del Pace
PhD student
Klejdja Xhani
Postdoctoral fellow
Woo Jin Kwon
Postdoctoral fellow
Francesco Scazza
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
Matteo Zaccanti

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