Lauriane Chomaz

Ultracold atomic gases offer a unique setting in which to explore how collective quantum phenomena emerge from the interactions between many particles. Their interactions, geometry, and dimensionality can be controlled with remarkable precision, making it possible to create and investigate forms of quantum matter that are difficult to access in conventional materials.

In this lecture, I will focus on gases of strongly magnetic atoms, where particles interact not only at short distances but also through long-range and anisotropic dipolar forces. The competition between these interactions produces surprisingly rich physics. One of the key discoveries of the past decade is that quantum fluctuations—usually thought of as small corrections to the average behavior of a system—can qualitatively change its fate, stabilizing states that would otherwise collapse. This mechanism has enabled the realization of self-bound quantum droplets and supersolids, an intriguing form of matter that combines the frictionless flow associated with superfluidity with the spatial order of a crystal.

I will introduce the basic physical mechanisms behind the emergence of these new states of matter and discuss how they can be created, observed, and characterized in experiments. I will then focus on supersolids and on the question of how their simultaneous crystalline and superfluid character reveals itself in their dynamics. Moving beyond the simplest supersolid states, I will then show how the interplay of competing interactions and quantum fluctuations can give rise to a variety of spatially ordered states. The possibility of tuning between these states gives access to structural phase transitions in the quantum regime, whose properties and universality can be explored and compared with those of their classical counterparts. I will conclude by discussing some of the open questions in this rapidly developing field and, more generally, the opportunities that dipolar quantum gases offer for exploring how new phases and collective phenomena emerge in interacting quantum systems.