paper

Consistent theory of self-bound quantum droplets with bosonic pairing

arXiv:2005.08581 · doi:10.1103/PhysRevLett.125.195302

Abstract

We revisit the Bogoliubov theory of quantum droplets proposed by Petrov {[}Phys. Rev. Lett. \textbf{115}, 155302 (2015){]} for an ultracold Bose-Bose mixture, where the mean-field collapse is stabilized by the Lee-Huang-Yang quantum fluctuations. We show that a loophole in Petrov's theory, i.e., the ignorance of the softening complex Bogoliubov spectrum, can be naturally removed by the introduction of bosonic pairing. The pairing leads to weaker mean-field attractions, and also stronger Lee-Huang-Yang term in the case of unequal intraspecies interactions. As a result, the equilibrium density for the formation of self-bound droplets significantly decrease in the deep droplet regime, in agreement with a recent observation from diffusion Monte Carlo simulations. Our construction of a consistent Bogoliubov theory paves the way to understand the puzzling low critical number of small quantum droplets observed in the experiment {[}Science \textbf{359}, 301 (2018){]}.

Minor changes thanks to the referee's reports; to appear in Physical Review Letters; Together with arXiv:2006.00434 [PRA 102, 043301 (2020)], arXiv:2006.05769 [PRA 102, 043302 (2020)] and arXiv:2007.00888 [to appear in New Journal of Physics], we present a bosonic pairing theory of quantum droplets in binary Bose mixtures

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