近日，德国海德堡大学物理研究所的Sandra Brandstetter&Philipp Lunt及其研究团队取得一项新进展。经过不懈努力，他们发现少数费米子原子的涌现相互作用驱动椭圆流。相关研究成果已于2025年1月2日在国际知名学术期刊《自然—物理学》上发表。
本文展示了一个包含少数强相互作用超冷原子的介观系统中椭圆流的出现。在这一系统中，由于所有相关长度尺度（系统尺寸、粒子间距和平均自由程）均相当，因此流体力学描述先验并不适用。实验中单粒子分辨率以及对粒子数和相互作用强度的确定性控制，使研究人员能够探索微观描述与流体力学框架之间的界限，并且研究人员证明了椭圆流是一种相互作用驱动的效应。这项研究结果表明，在流体力学通常不适用的情形下，集体行为仍然可以出现。
据悉，流体力学是一个成功的框架，能够有效描述从亚核尺度到宇宙尺度等复杂多体系统的动力学。它通过对系统微观成分的粗粒化假设来定义宏观流体元，这些流体元相对于粒子间距和平均自由程而言是较大的。在高能重离子碰撞中，人们从椭圆流的观测中推断出了流体动力学行为，椭圆流即粒子动量分布的椭圆形变。
附：英文原文
Title: Emergent interaction-driven elliptic flow of few fermionic atoms
Author: Brandstetter, Sandra, Lunt, Philipp, Heintze, Carl, Giacalone, Giuliano, Heyen, Lars H., Gaka, Maciej, Subramanian, Keerthan, Holten, Marvin, Preiss, Philipp M., Floerchinger, Stefan, Jochim, Selim
Issue&Volume: 2025-01-02
Abstract: Hydrodynamics is a successful framework for effectively describing the dynamics of complex many-body systems, ranging from subnuclear to cosmological scales. It applies coarse-grained assumptions about the microscopic constituents of a system to define macroscopic fluid cells, which are large compared to the interparticle spacing and mean free path. In high-energy heavy-ion collisions, hydrodynamic behaviour is inferred from the observation of elliptic flow, which is the elliptical deformation of the particle momentum distribution. Here we demonstrate the emergence of elliptic flow in a mesoscopic system with a few strongly interacting ultracold atoms. In our system, a hydrodynamic description is a priori not applicable, as all relevant length scales—the system size, the interparticle spacing and the mean free path—are comparable. The single-particle resolution and the deterministic control over the number of particles and interaction strength in our experiment allow us to explore the boundaries between a microscopic description and a hydrodynamic framework, and we show that elliptic flow appears as an interaction-driven effect. Our results demonstrate the emergence of collective behaviour in a regime where hydrodynamics is not usually applicable.
DOI: 10.1038/s41567-024-02705-8
Source: https://www.nature.com/articles/s41567-024-02705-8