Quantum liquid droplets in a mixture of Bose-Einstein condensates

Cesar R. Cabrera, Luca Tanzi, Sanz, J. +4 more

Bose-Einstein condensates

Zhichao Guo, Fan Jia, Lintao Li +1 more

Abdulla Rakhimov, Sh. Mardonov

C. R. Cabrera, L. Tanzi, J. Sanz +4 more

Quantum droplets are small clusters of atoms self-bound by the balance of attractive and repulsive forces. Here, we report on the observation of droplets solely stabilized by contact interactions in a mixture of two Bose-Einstein condensates. We demonstrate that they are several orders of magnitude more dilute than liquid helium by directly measuring their size and density via in situ imaging. We show that the droplets are stablized against collapse by quantum fluctuations and that they require a minimum atom number to be stable. Below that number, quantum pressure drives a liquid-to-gas transition that we map out as a function of interaction strength. These ultradilute isotropic liquids remain weakly interacting and constitute an ideal platform to benchmark quantum many-body theories.

Fabian Böttcher, Jan-Niklas Schmidt, Jens Hertkorn +5 more

Quantum fluctuations can stabilize Bose-Einstein condensates (BEC) against the mean-field collapse. Stabilization of the condensate has been observed in quantum degenerate Bose-Bose mixtures and dipolar BECs. The fine-tuning of the interatomic interactions can lead to the emergence of two new states of matter: liquid-like self-bound quantum droplets and supersolid crystals formed from these droplets. We review the properties of these exotic states of matter and summarize the experimental progress made using dipolar quantum gases and Bose-Bose mixtures. We conclude with an outline of important open questions that could be addressed in the future.

Khelifa Mohammed Elhadj, Laila Y. Al Sakkaf, Abdelâali Boudjemâa +1 more