Self-bound states appear in contexts as diverse as solitary waves in channels, optical solitons in non-linear media and liquid droplets. Their binding results from a balance between attractive forces, which tend to make the system collapse, and repulsive ones, which stabilize it to a finite size. In this talk, I will present our recent experiments on dilute quantum liquid droplets: macroscopic clusters of ultra-cold atoms that are eight orders of magnitude more dilute than liquid Helium, but have similar liquid-like properties. We have observed for the first time these droplets in a mixture of Bose-Einstein condensates with effective attractive interactions, and mapped out the associated liquid-to-gas transition [C. R. Cabrera et al., Science 359, 301 (2018)]. In a second series of experiments, we have placed such droplets in an optical waveguide and explored their connection to more conventional bright solitons [P. Cheiney et al., Phys. Rev. Lett. in press]. Interestingly, the existence of dilute quantum droplets is a direct result of quantum fluctuations. Thus, their properties constitute a sensitive test of quantum many-body theories.


Wednesday, March 21, 2018, 15:00. ICFO Auditorium