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.

Shining a blue detuned thin (2 μm) barrier we produce a double-well potential, which creates a Josephson-like junction for fermionic superfluids. By varying the interactions we investigate the population and phase dynamics between the two wells, observing the Josephson effect across the BEC-BCS crossover.

G. Valtolina et al.,
Josephson effect in fermionic superfluids across the BEC-BCS crossover
Science 350, 1505 (2015)

Using the inverse Abel transform, the in-situ 3D density profile of a cloud of two-state 6Li atoms trapped in a potential with cylindrical symmetry can be derived. Following [M. Ku et al., Science 335, 563 (2012)] we reconstruct the equation of state of the system. In particular, local pressure and compressibility have been obtained for the unitary Fermi gas, revealing the superfluid transition.

The quest to develop new and efficient experimental schemes to produce large and highly degenerate fermionic samples is fundamental in the way of using them to study fermionic superfluidity with a high degree of control on properties as interaction strength and dimensionality. 6Li samples of two spin components offers a broad Feshbach resonance allowing a good tenability of the interactions and the ability to investigate superfluidity across the BEC-BCS crossover. On the other way, standard laser cooling configurations are not efficient due to the lack of sub-Doppler cooling mechanism on the D2 line. We use a gray molasses operating on the D1 atomic transition to produce degenerate quantum gases of 6Li with a large number of atoms. This sub-Doppler cooling phase allows us to lower the initial temperature of 109 atoms from 500 to 40 μK in 2 ms. We observe that D1 cooling remains effective into a high-intensity infrared dipole trap where two-state mixtures are evaporated to reach the degenerate regime. We produce molecular Bose-Einstein condensates of up to 5×105 molecules and weakly interacting degenerate Fermi gases of 7×105 atoms at T/TF

A. Burchianti et al.
Efficient all-optical production of large 6Li quantum gases using D1 gray-molasses cooling
Phys. Rev. A 90, 043408 (2014)

We aim at studying two-dimensional fermionic 6Li atoms across the BCS-BEC crossover. We plan to benefit of the recent advances in ultracold atomic systems, such as single-site addressability and the full control of the interparticle interactions. Tailoring arbitrary optical potentials will create the perfect environment for implementing quantum models. In particular, we want to characterize the superfluid phase by studying the interlayer tunneling, discriminating the coherent Josephson dynamics from the single-particle hopping. By adding disorder we will simulate the physics of granular superconductors, testing the robustness of the order parameter and the onset of metallic phases at higher temperatures.

The Lithium Lab is funded by ERC Consolidator Grant "QuFerm2D: Quantum Simulation of two-dimensional fermionic systems" awarded in 2012 to Giacomo Roati.

Li people

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

Li contacts

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

Giacomo Roati
(roati@lens.unifi.it)

Li funding