Marek Gluza"This setup is so cool, we had to rejuvenate it for two years and then for a year we were steadlily acquiring data. We have perks that somebody 10 years ago made possible because maybe somebody would need them." ~ roughly the chat with Cosetta Baroni.
In fact it was a 90 minute masterclass in #ColdAtoms 🙏🙏🙏: they tune the interaction of Li and K using Feshbach resonances, have Rabbi interference for tuning the state allowing for selective readout, and by choosing the isotope they can have either bosons or fermions dragging as polarons in a Fermi sea oh btw which is polarized by several Gauss magnetic field controlled to mili Gauss.
Mediated interactions between Fermi polarons and the role of impurity quantum statistics
The notion of quasi-particles is essential for understanding the behaviour of complex many-body systems. A prototypical example of a quasi-particle, a polaron, is an impurity strongly interacting with a surrounding medium. Fermi polarons, created in a Fermi sea, provide a paradigmatic realization of this concept. As an inherent and important property such quasi-particles interact with each other via modulation of the medium. While quantum simulation experiments with ultracold atoms have significantly improved our understanding of individual polarons, the detection of their interactions has remained elusive in these systems. Here, we report the unambiguous observation of mediated interactions between Fermi polarons consisting of K impurities embedded in a Fermi sea of Li atoms. Our results confirm two landmark predictions of Landau's Fermi-liquid theory: the shift of the polaron energy due to mediated interactions, linear in the concentration of impurities, and its sign inversion with impurity quantum statistics. For weak to moderate interactions between the impurities and the medium, we find excellent agreement with the static (zero-momentum and energy) predictions of Fermi-liquid theory. For stronger impurity-medium interactions, we show that the observed behaviour at negative energies can be explained by a more refined many-body treatment including retardation and molecule formation