Lauriane Chomaz: "Ultracold dipolar Bose gases of magnetic atoms: roton excitations, quantum stabilization, droplets and supersolid states"
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M7-411
ENS Lyon
Thanks to their high degree of control and tunability, ultracold atomic gases provide a rich platform for the study of quantum many-body effects. Ultracold gases of highly magnetic atoms exhibit unique interaction properties that lead to striking behaviors, both at the mean-field level and beyond [1]. At mean field, depending on the gas geometry, the competition of contact and long-range dipolar interaction may yield novel excitation features, including a roton mode reminiscent of the physics of superfluid helium, and modifies the stability of the system. Furthermore, a universal stabilization mechanism driven by beyond mean field effects and preventing the gas to collapse at the mean-field instability was experimentally discovered a decade ago. This mechanism allows the emergence of exotic states of matter, including ultradilute quantum droplets, crystallized quantum states, and – most notably – supersolids, which combine the seemingly antithetical properties of superfluids and solids [2].
In my talk, I will review the physics of dipolar quantum Bose gases, including roton excitations, stabilization beyond mean field, and stabilized states. I will outline the theoretical description of these systems via an effective mean-field treatment, including the effect of quantum fluctuations via an effective higher-order interaction. I will describe the seminal observations of these phenomena in gases of magnetic atoms and how they were made possible from the long-standing progress in the field. I will present our current understanding of the properties of the stabilized states and in particular of dipolar supersolids, as well as the ongoing research in my group at Heidelberg University, where we explore quantum phase transitions between dipolar supersolids with different crystal organization [3].
References
[1] L. Chomaz et al., "Dipolar physics: A review of experiments with magnetic quantum gases," Reports on Progress in Physics 86, 026401 (2023)
[2] L. Chomaz, "Quantum-stabilized states in magnetic dipolar quantum gases." Annual Review of Condensed Matter Physics 17 (2025)
[3] K. Chandrashekara et al., in preparation (2026)