Quantum Droplets in a Mixture of Bose–Fermi Superfluids
Jing-Bo Wang1, Jian-Song Pan2, Xiaoling Cui3,4*, and Wei Yi1,5*
1CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China 2Department of Physics, National University of Singapore, Singapore 117542, Singapore 3Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China 4Songshan Lake Materials Laboratory, Dongguan 523808, China 5CAS Center For Excellence in Quantum Information and Quantum Physics, Hefei 230026, China
Abstract：We study the formation of quantum droplets in the mixture of a single-component Bose–Einstein condensate (BEC), and a two-species Fermi superfluid across a wide Feshbach resonance. With repulsive boson-boson and attractive boson-fermion interactions, we show that quantum droplets can be stabilized by attractive fermion-fermion interactions on the Bardeen–Cooper–Schrieffer (BCS) side of the resonance, and can also exist in the deep BEC regime under weak boson-fermion interactions. We map out the phase diagram for stable droplets with respect to the boson-boson and boson-fermion interactions, and discuss the role of different types of quantum fluctuations in the relevant regions of the BCS-BEC crossover. Our work reveals the impact of fermion pairing on the formation of quantum droplets in Bose–Fermi mixtures, and provides a useful guide for future experiments.
2020, Vol. 37 
