近日，意大利弗洛伦萨大学的D. Hernández-Rajkov及其研究团队取得一项新进展。经过不懈努力，他们揭示环形原子超流体中剪切流与涡旋阵列不稳定性的联系。相关研究成果已于2024年3月27日在国际知名学术期刊《自然—物理学》上发表。
该研究团队深入观察了两个反向旋转的原子超流体之间的接触界面，发现其逐渐发展成有序的量子化涡旋环形阵列，随后失去稳定性并卷曲成涡旋团簇。研究人员进一步提取了不稳定性增长率，并揭示这些增长率在不同超流体状态下遵循相同的标度关系，涵盖了从弱相互作用玻色子到强关联费米子对凝聚的广泛范围。
这项重要研究不仅建立了涡旋阵列与剪切流动不稳定之间的紧密联系，还提出了一种合理解释：观测到的量子化涡旋动力学正是潜在不稳定流动的一种外在表现。此外，这些发现为探索非平衡现象，如涡旋物质相变和二维量子湍流的自发出现与衰变，开辟了新的研究路径。
据悉，在相对运动的两层流体之间的界面上，微小的波动可以被指数放大，从而引起涡量和层流的破裂。尽管经典流体中的剪切流动不稳定性已在多种情境中得到了广泛观测，但在量子化环流存在的情况下进行的控制实验却相当稀少。
附：英文原文
Title: Connecting shear flow and vortex array instabilities in annular atomic superfluids
Author: Hernnadez-Rajkov, D., Grani, N., Scazza, F., Del Pace, G., Kwon, W. J., Inguscio, M., Xhani, K., Fort, C., Modugno, M., Marino, F., Roati, G.
Issue&Volume: 2024-03-27
Abstract: At the interface between two fluid layers in relative motion, infinitesimal fluctuations can be exponentially amplified, inducing vorticity and the breakdown of laminar flow. While shear flow instabilities in classical fluids have been extensively observed in various contexts, controlled experiments in the presence of quantized circulation are quite rare. Here we observe how the contact interface between two counter-rotating atomic superflows develops into an ordered circular array of quantized vortices, which loses stability and rolls up into vortex clusters. We extract the instability growth rates and find that they obey the same scaling relations across different superfluid regimes, ranging from weakly interacting bosonic to strongly correlated fermionic pair condensates. Our results establish connections between vortex arrays and shear flow instabilities, suggesting a possible interpretation of the observed quantized vortex dynamics as a manifestation of the underlying unstable flow. Moreover, they open the way for exploring out-of-equilibrium phenomena such as vortex matter phase transitions and the spontaneous emergence and decay of two-dimensional quantum turbulence.
DOI: 10.1038/s41567-024-02466-4
Source: https://www.nature.com/articles/s41567-024-02466-4