At the interface between two fluid layers in relative motion, infinitesimal fluctuations can be exponentially amplified, inducing vorticity and the breakdown of laminar flow. While shear-flow instabilities in classical fluids have been extensively observed in various contexts, controlled experiments in the presence of quantized circulation are quite rare. In our last work, we observe how the contact interface between two counter-rotating atomic superflows develops into an ordered circular array of quantized vortices, which loses stability and rolls up into vortex clusters. We extract the instability growth rates and find that they obey the same scaling relations across different superfluid regimes, ranging from weakly-interacting bosonic to strongly-correlated fermionic pair condensates. Our results establish connections between vortex arrays and shear-flow instabilities, suggesting a possible interpretation of the observed quantized vortex dynamics as a manifestation of the underlying unstable flow. Moreover, they open the way for exploring out-of-equilibrium phenomena such as vortex-matter phase transitions and the spontaneous emergence and decay of two-dimensional quantum turbulence.

D. Henández-Rajkov et al.
Connecting shear-flow and vortex array instabilities in annular atomic superfluids
Nat. Phys. (2024)

We have completed the optical setup for the 689 nm laser source that will be employed for further cool the Strontium atoms by a factor of 1000 in a red 3D MOT, in order to reach a temperature of few micro Kelvin. A significant challenge we faced was stabilizing the frequency of the red laser to a very stable and very high finesse ultra-low expansion cavity.

We are immensely proud of Giulio Biagioni, who has defended his doctoral thesis "Can a superfluid be solid? A study of the supersolid phase in a dipolar quantum gas", achieving the summa cum laude distinction. In the last few years, Giulio has given invaluable contributions to our research, enriching our group in countless ways and inspiring many experiments. We wish him all the success and fulfillment he deserves, and even more luck in his academic journey!

See also the thesis

Beatrice successfully defends her Master's thesis titled ["Realization and characterization of LiCr ultracold bosonic dimers"], and starts her PhD on few-body physics and impurity problems in resonantly interacting Fermi mixtures.

Congrats and good luck Bea!

We are thrilled to welcome Dr. Chiara Mazzinghi to our team! Chiara brings a wealth of expertise and fresh perspectives to our group. We look forward to the exciting collaborations ahead and the innovative ideas she will contribute!