报告时间：2023年6月25日（周日）上午10：30

报告地点：龙赛理科楼北楼228会议室

报告人：胡辉 （副教授，斯威本技术大学）

报告人简介：

胡辉，2001清华大学博士；2001-2004意大利国际理论物理中心和比萨高师博士后；2005澳大利亚昆士兰大学访问学者；2006-2008中国人民大学物理系责任教授；2009-2017获澳大利亚研究理事会人才计划女皇伊丽莎白二世基金（QE II Fellowship）和未来研究员基金（Future Fellowship）在斯威本技术大学从事科研教学。2011至今为该校副教授。主要从事超冷原子气体的研究。在过去二十多年，对量子流体理论，包括强相互作用的费米气体和玻色爱因斯坦凝聚体方面，做出了若干贡献。至今，共发表学术论文一百八十余篇。现为亚太物理学会开源期刊AAPPS Bulletin编辑，美国物理学会开源期刊Physical Review Research编委，以及澳大利亚研究理事会College of Experts成员。

报告摘要：

Over the past few years, a newly discovered phase of ultracold, dilute quantum droplets has attracted increasingly attention in different fields of physics. In sharp contrast to other gas-like phases in containers, quantum droplets are self-bound, liquid-like clusters of ten to hundred thousand of atoms in free space, formed by the delicate balance between the attractive mean-field force and repulsive force from quantum fluctuations.

Here, I will give our theoretical progress on quantum droplets in two-component Bose-Bose mixtures. We revisit the Bogoliubov theory of quantum droplets proposed by Petrov [1], 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 [2]. The pairing leads to weaker mean-field attractions, and 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 decreases in the deep droplet regime, in agreement with a recent observation from diffusion Monte Carlo simulations. Our construction of a consistent pairing theory of ultradilute quantum droplet may also be relevant to understand the supersolid in dipolar gases. Further, by considering both attractive two-body interaction and repulsive three-body interaction, we determine a rich phase diagram for three-body interacting droplets and show the existence of a tri-critical point, where the three phase – quantum droplet, superfluid gas, and normal gas – meet together [3].

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