Quantum Criticality of Liquid-Gas Transition in a Binary Bose Mixture

• Published in: Physical review letters Vol. 130; no. 19; p. 193001
• Main Authors: He, Li, Li, Haowei, Yi, Wei, Yu, Zeng-Qiang
• Format: Journal Article
• Language: English
• Published: United States 12.05.2023
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.130.193001

Quantum liquid, in the form of a self-bound droplet, is stabilized by a subtle balance between the mean-field contribution and quantum fluctuations. While a liquid-gas transition is expected when such a balance is broken, it remains elusive whether liquid-gas critical points exist in the quantum regime. Here, we study the quantum criticality in a binary Bose mixture undergoing the liquid-gas transition. We show that, beyond a narrow stability window of the self-bound liquid, a liquid-gas coexistence persists, which eventually transits into a homogeneous mixture. Importantly, we identify two distinct critical points where the liquid-gas coexistence terminates. These critical points are characterized by rich critical behaviors in their vicinity, including divergent susceptibility, unique phonon-mode softening, and enhanced density correlations. The liquid-gas transition and the critical points can be readily explored in ultracold atoms confined to a box potential. Our work highlights the thermodynamic approach as a powerful tool in revealing the quantum liquid-gas criticality, and paves the way for further studies of critical phenomena in quantum liquids.