Can a superfluid be solid? A study of the supersolid phase of matter in a dipolar quantum gas

The thesis reports the experimental study of a dipolar quantum gas of bosonic atoms. At ultra-low temperatures, the system is a Bose-Einstein condensate. Changing the interactions between the atoms, a density modulation forms on the condensate, adding crystal-like properties to the superfluid. This exotic quantum phase is a so-called supersolid, a phase of matter theoretically investigated for more than 50 years and only recently realized in an experimental platform. In my thesis, I report the experiments I realized to characterize and understand the supersolid phase. They include the exploration of the superfluid-supersolid quantum phase transitions, the measurements of the moment of inertia and superfluid fraction of the supersolid, and the demonstration of a self-induced Josephson effect between supersolid clusters. All these phenomena are peculiar to the supersolid phase and distinguish it from superfluids and ordinary crystals.