近日，美国麻省理工学院的Martin Zwierlein及其研究团队取得一项新进展。经过不懈努力，他们揭示浸没在玻色-爱因斯坦凝聚体中费米子杂质的集体流动。相关研究成果已于2024年6月21日在国际知名学术期刊《自然—物理学》上发表。

本文探讨了浸没在玻色-爱因斯坦凝聚体中的自旋极化费米子杂质的集体振荡行为，并深入分析了其与相互作用强度和温度之间的关系。在强相互作用条件下，费米气体精确地模拟了凝聚体的超流体流体动力学模式，这些模式涵盖了从低能四极模式到高阶法拉第激发的广泛范围。随着玻色子热激发的逐渐增强，杂质的动力学特性从无碰撞状态逐渐过渡到流体动力学状态，这一转变过程与二维电子流体中流体动力学的出现相类似。

据悉，玻色子和费米子相互作用的混合物在自然界中无处不在。它们构成了物理学标准模型的支柱，为理解量子材料提供了一个框架，在氦稀释制冷机中具有重要的技术意义。然而，描述它们的耦合热力学和集体行为是具有挑战性的。超冷原子的玻色-费米混合物提供了一个平台，可以在高度可控的环境中研究它们的性质，在这种环境中，物质浓度和相互作用强度可以任意调节。

附：英文原文

Title: Collective flow of fermionic impurities immersed in a Bose–Einstein condensate

Author: Yan, Zoe Z., Ni, Yiqi, Chuang, Alexander, Dolgirev, Pavel E., Seetharam, Kushal, Demler, Eugene, Robens, Carsten, Zwierlein, Martin

Issue&Volume: 2024-06-21

Abstract: Interacting mixtures of bosons and fermions are ubiquitous in nature. They form the backbone of the standard model of physics, provide a framework for understanding quantum materials and are of technological importance in helium dilution refrigerators. However, the description of their coupled thermodynamics and collective behaviour is challenging. Bose–Fermi mixtures of ultracold atoms provide a platform to investigate their properties in a highly controllable environment, where the species concentration and interaction strength can be tuned at will. Here we characterize the collective oscillations of spin-polarized fermionic impurities immersed in a Bose–Einstein condensate as a function of the interaction strength and temperature. For strong interactions, the Fermi gas perfectly mimics the superfluid hydrodynamic modes of the condensate, from low-energy quadrupole modes to high-order Faraday excitations. With an increasing number of bosonic thermal excitations, the dynamics of the impurities cross over from the collisionless to the hydrodynamic regime, reminiscent of the emergence of hydrodynamics in two-dimensional electron fluids.

DOI: 10.1038/s41567-024-02541-w

Source: https://www.nature.com/articles/s41567-024-02541-w