Supersolidity in the ultracold: when atoms behave as solid and superfluid at the same time

Ultracold quantum gases are both an ideal test-bed platform to address key questions in quantum physics and a powerful resource to realize novel paradigms and novel phases of quantum matter. Moreover, the potential of such systems is becoming ever more enabling as scientists acquire an increasingly fine control over optical manipulation and inter-particle interactions.
Recently, a novel class of atomic species, possessing an exceptionally strong magnetic character is entering the stage, offering a new conceptual twist for the field. In our laboratories in Innsbruck, we have realized the first dipolar Bose-Einstein condensate and Fermi gas of the highly magnetic Erbium species and the first dipolar quantum mixture of Erbium and Dysprosium.
I will report on our recent observations of the elusive and paradoxical supersolid state of quantum matter, using both Erbium and Dysprosium ultracold gases. Such paradoxical phase, in which crystal rigidity and superfluid flow coexist, has intrigued scientists across different disciplines for decades. It now became possible to create supersolidity in the ultracold thanks to the unique interplay between long-range dipolar interactions, contact interactions, and a powerful stabilization mechanism based on quantum fluctuations.