The newly created Cr/Li team at CNR-INO could indeed successfully pursue a major part of the ambitious PoLiChroM plan within the project duration.
A prime effort of the PoLiChroM team focused on setting up a new cold-atom to produce the first chromium-lithium ultracold mixture worldwide. Nowadays, the experimental machine of the Cr/Li lab is able to produce samples of more than 10^5 chromium and 10^6 lithium ultracold fermionic atoms. Successful search for interspecies Feshbach resonances in this novel mixture guarantees the precise control over Cr-Li interactions. These achievements, subject of one recent Physical Review A publication, plus four ones currently in preparation, will guarantee the successful pursuit of resonant three-body forces and novel few-body cluster states (GOAL1) in chromium-lithium mixtures within the forthcoming year.
During the project period, we could thoroughly and successfully address GOAL3 and GOAL2 of PoLiChroM, namely the investigation of ferromagnetism in repulsive Fermi mixtures, and the search for exotic superfluidity in highly correlated ultracold Fermi mixtures.
By means of novel strategies only partially envisioned at the start of the project, PoLiChroM enabled to clarify the intricate many-body dynamics of repulsive Fermi mixtures. We unveiled the existence of a ferromagnetic instability, and gained important information about the interplay between ferromagnetism and pairing in these systems (GOAL3). Our surveys also disclosed an exotic heterogeneous phase, where spin-polarized atoms and pairs macroscopically coexist, arranged in spatially-separated micro-domains. Superfluidity in such an inhomogeneous system could not be demonstrated, yet, but this finding is crucially relevant in the context of GOAL2 of PoLiChroM. These studies, leading to five publications (including 1 Nature Physics and 3 Physical Review Letters), also allowed me to establish a strong collaboration with the Nobel Laureate Prof. W. Ketterle.
Upon developing an innovative theoretical framework, PoLiChroM allowed for a thorough characterization of resonantly interacting Fermi superfluids through Josephson transport measurements. Building on a theoretical model developed with Prof. W. Zwerger, together with Dr. G. Roati at CNR-INO we could measure the “current-voltage” characteristics of an atomic Josephson junction made of Fermi superfluids of lithium atoms. From the Josephson supercurrent measure, we could extract the superfluid order parameter throughout the BCS-BEC crossover. These surveys, highly relevant for PoLiChroM GOAL2, yielded four high-impact publications, including 1 Science and 2 Phys. Rev. Lett.
