中国物理B ›› 2021, Vol. 30 ›› Issue (1): 10306-.doi: 10.1088/1674-1056/abd2ad

所属专题: SPECIAL TOPIC — Ultracold atom and its application in precision measurement

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  • 收稿日期:2020-10-28 修回日期:2020-12-09 接受日期:2020-12-11 出版日期:2020-12-17 发布日期:2020-12-30

Ultradilute self-bound quantum droplets in Bose-Bose mixtures at finite temperature

Jia Wang(王佳), Xia-Ji Liu(刘夏姬), and Hui Hu(胡辉)†   

  1. Centre for Quantum Technology Theory, Swinburne University of Technology, Melbourne, Victoria 3122, Australia
  • Received:2020-10-28 Revised:2020-12-09 Accepted:2020-12-11 Online:2020-12-17 Published:2020-12-30
  • Contact: Corresponding author. E-mail: hhu@swin.edu.au
  • Supported by:
    Project supported by the Australian Research Council's (ARC) Discovery Program (Grant Nos. DE180100592 and DP190100815), (Grant No. DP180102018), and (Grant No. DP170104008).

Abstract: We theoretically investigate the finite-temperature structure and collective excitations of a self-bound ultradilute Bose droplet in a flat space realized in a binary Bose mixture with attractive inter-species interactions on the verge of mean-field collapse. As the droplet formation relies critically on the repulsive force provided by Lee-Huang-Yang quantum fluctuations, which can be easily compensated by thermal fluctuations, we find a significant temperature effect in the density distribution and collective excitation spectrum of the Bose droplet. A finite-temperature phase diagram as a function of the number of particles is determined. We show that the critical number of particles at the droplet-to-gas transition increases dramatically with increasing temperature. Towards the bulk threshold temperature for thermally destabilizing an infinitely large droplet, we find that the excitation-forbidden, self-evaporation region in the excitation spectrum, predicted earlier by Petrov using a zero-temperature theory, shrinks and eventually disappears. All the collective excitations, including both surface modes and compressional bulk modes, become softened at the droplet-to-gas transition. The predicted temperature effects of a self-bound Bose droplet in this work could be difficult to measure experimentally due to the lack of efficient thermometry at low temperatures. However, these effects may already present in the current cold-atom experiments.

Key words: Bose-Einstein condensation, quantum droplet

中图分类号: 

  • 03.75.-b
03.75.Kk (Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow)