电子流体中涡旋的直接观测
Direct observation of vortices in an electron fluid
摘要：
涡流是流体动力学流动的标志。最近的研究表明，超纯导体中的强相互作用电子可以显示出流体动力学行为的特征，包括负非局部电阻，窄通道中的Poiffille流以及违反Wiedemann-Franz定律。在这里，我们提供了第一个可视化的电子流体中的电子池。通过利用纳米级扫描超导量子干涉装置的尖端（SQUID的尖端上），我们图像的电流分布在一个圆形的腔室连接通过一个小孔到相邻的窄载流带在高纯度II型外尔半金属WTe 2。在这种几何结构中，Gurzhi动量扩散长度和孔径的大小决定了涡旋稳定性相图。我们发现，涡流是目前只为小孔径，而流量是层流（非涡流）较大的孔径，符合理论分析的流体动力学制度，并在相反的预期弹道输运在WTe 2在低温下。此外，附近的旋涡层流过渡，我们观察到一个单一的涡流室分裂成两个涡流，一个行为，只能发生在流体动力学制度，不能持续的弹道输运。这些发现提出了一种新的流体动力学流动机制：在低温下变得非常弱的体相电子-电子散射，而不是通常认为的电子-电子散射，载流子动量的空间扩散是通过薄纯晶体平面表面的小角度散射实现的。这种表面诱导的准流体动力学为在高迁移率电子系统中探索和利用电子流体学开辟了新的途径。
英文摘要：
Vortices are the hallmarks of hydrodynamic flow. Recent studies indicate that strongly-interacting electrons in ultrapure conductors can display signatures of hydrodynamic behavior including negative nonlocal resistance, Poiseuille flow in narrow channels, and a violation of the Wiedemann-Franz law. Here we provide the first visualization of whirlpools in an electron fluid. By utilizing a nanoscale scanning superconducting quantum interference device on a tip (SQUID-on-tip) we image the current distribution in a circular chamber connected through a small aperture to an adjacent narrow current carrying strip in high-purity type-II Weyl semimetal WTe2. In this geometry, the Gurzhi momentum diffusion length and the size of the aperture determine the vortex stability phase diagram. We find that the vortices are present only for small apertures, whereas the flow is laminar (non-vortical) for larger apertures, consistent with the theoretical analysis of the hydrodynamic regime and in contrast to the expectations of ballistic transport in WTe2 at low temperatures. Moreover, near the vortical-to-laminar transition, we observe a single vortex in the chamber splitting into two vortices, a behavior that can occur only in the hydrodynamic regime and cannot be sustained by ballistic transport. These findings suggest a novel mechanism of hydrodynamic flow: instead of the commonly considered electron-electron scattering at the bulk, which becomes extremely weak at low temperatures, the spatial diffusion of charge carriers' momenta is enabled by small-angle scattering at the planar surfaces of thin pure crystals. This surface-induced para-hydrodynamics opens new avenues for exploring and utilizing electron fluidics in high-mobility electron systems.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
