Taming, slowing and trapping atoms with light
Cold is quantum, Quantum is cool!
We shape quantum matter
Multicolored lasers for a variety of atoms
Keeping our eyes on the quantum world
Join our ultracool group!
High technology for great science

Welcome to the website of the Ultracold Quantum Gases group at the European Laboratory for Nonlinear Spectroscopy (LENS), the Department of Physics and Astronomy of the University of Florence (Italy) and the Institute of Optics of the Italian National Research Council (CNR - INO). In our labs we use lasers and magnetic fields to produce the lowest temperatures of the Universe, just a few billionths of a degree above absolute zero...

At these temperatures, atoms stop moving and we can control them for a variety of different fundamental studies and applications. We can force atoms to arrange according to a periodic structure and simulate the behavior of crystalline solids and new materials. We can use the atoms as ultra-high accurate sensors to probe forces with the power of quantum mechanics. We can study how quantum particles combine together under the action of strong interactions and how superfluidity develops. We can use these ultracold atoms to process information and develop new quantum technologies.

Dress warmly and... follow us for this ultracold journey!


A key manifestation of superfluidity in liquids and gases is a reduction of the moment of inertia under slow rotations. Non-classical rotational effects have been searched for a long time also for the elusive supersolid phase of matter, in which superfluidity coexists with a lattice structure. Here we show that the recently discovered supersolid phase in dipolar quantum gases features a reduced moment of inertia. We study a peculiar rotational oscillation mode in a harmonic potential, the scissors mode, already employed for superfluids. From the measured moment of inertia, we derive a superfluid fraction in analogy with the original definition by A. J. Leggett. The superfluid fraction is different from zero and of order of unity, providing direct evidence of the superfluid nature of the dipolar supersolid. A qualitative comparison with the original theoretical model supports the observation of a large superfluid fraction close to the transition from the Bose-Einstein condensate (BEC) and the supersolid.

L. Tanzi, et al.
Evidence of superfluidity in a dipolar supersolid from non-classical rotational inertia
Science 371, 1162 (2021)

By investigating the tunneling transport of ultracold atomic Fermi gases, we reveal for the first time a peculiar enhancement of the conductance of neutral superfluids, in contrast with charged superconductors. — Both superfluids and superconductors owe their distinctive frictionless flow to their condensed nature, namely the macroscopic occupation of a single quantum state. Regardless of the electric charge of the constituent particles, condensation results in the emergence of the Josephson effect: a tunneling current flows when two superfluid reservoirs are coupled with one another through a thin insulating barrier in a so-called Josephson junction.
Exactly as their superconducting counterparts, fermionic superfluids composed of ultracold atoms can support the flow of a dissipationless current through the junction up to a maximum value. This maximum Josephson current is directly connected to the condensate density, as we demonstrated in a previous study in the low-temperature limit, and extended in this work to finite temperatures across the superfluid transition.
For higher currents instead, the junction behaves resistively, giving rise to a finite Ohmic conductance, which we find to massively exceed the value observed in charged electronic junctions. Such large anomalous conductance, fostered by the condensate coupling with sound wave excitations, is tightly linked to charge neutrality boosting particle transport through the junction. This behavior is indeed absent in electronic junctions, where Coulomb interactions inhibit sound waves and the conductance is essentially given by the tunneling of non-condensed particles.

G. Del Pace et al.
Tunneling Transport of Unitary Fermions across the Superfluid Transition
Phys. Rev. Lett. 126, 055301 (2021)

It is a great privilege for us to welcome Nigel Cooper, Professor in Theoretical Physics of University of Cambridge. Prof. Cooper will honour us with his presence for one year as a Visiting Professor of the Department of Physics and Astronomy of the University of Florence.
The research interests of Prof. Cooper are focused on the nature and properties of the novel phases of matter that can emerge as a result of quantum mechanical effects in interacting many-particle systems. In particular, he is a world leader in the investigation of the role of topology in the collective properties of ultra-cold atomic gases and of the electronic properties of novel solid state materials. He was awarded the 2007 Maxwell Medal and Prize by the Institute of Physics, a Humboldt Research Award (2013), an EPSRC Established Career Fellowship (2013), a Simons Investigator Award (2017) and the 2019 Lord Rayleigh Prize of the IOP.

We are very grateful to him and looking forward to inspiring discussions and collaborations. We wish him a very pleasant and productive stay at University of Florence and LENS!

We have experimentally and theoretically studied how the interactions affect the interference pattern of two expanding 87Rb condensates. Our analysis shows that the condensate phase is modified by the mutual interaction only in the region where the wave packets overlap. This result proves that the general assumption of phase rigidity has to be abandoned for an accurate description of matter-wave interference.

A. Burchianti et al.
Effect of interactions in the interference pattern of Bose-Einstein condensates
Phys. Rev. A 102, 043314 (2020)

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Seminars & Events

Seminar by Prof. Carlos Sa de Melo:
Ultra-cold Fermi Gases with Three and Four Internal States: The Evolution from BCS to BEC Superfluidity in Multiband Systems ,
h. 12.00 Querzoli room, LENS.
Seminar by Dr. Dimitrios Trypogeorgos:
Unconventional topology with a Rashba spin-orbit coupled quantum gas,
h. 14.30 Querzoli room, LENS.
Firenze-Trieste workshop:
Two days of talks and scientific discussions with the theory groups of ICTP and SISSA,
ICTP, Trieste.
Firenze-Trieste workshop:
Two days of talks and scientific discussions with the theory groups of ICTP and SISSA,
Aula Querzoli, LENS.
Quantumgases retreat:
A full-day group meeting to discuss the activity of the different labs,
h. 9.00 Villa il Gioiello, Arcetri.
Fermi Colloqium by Prof. Wolfgang Ketterle:
New forms of matter with ultracold atoms: superfluids, supersolids and more,
h. 11.30 Querzoli room, LENS.
Seminar by Prof. Arno Rauschenbeutel:
Chiral Quantum Optics,
h. 11.00 Querzoli room, LENS.
The LENS QuantumGases group is glad to welcome in Florence Prof. Randall Hulet from Rice University. Prof. Hulet will be our guest for one month until mid July.