论文标题

直接观察电子流体中的涡旋

Direct observation of vortices in an electron fluid

论文作者

Aharon-Steinberg, Amit, Völkl, Tobias, Kaplan, Arkady, Pariari, Arnab K., Roy, Indranil, Holder, Tobias, Wolf, Yotam, Meltzer, Alexander Y., Myasoedov, Yuri, Huber, Martin E., Yan, Binghai, Falkovich, Gregory, Levitov, Leonid S., Hücker, Markus, Zeldov, Eli

论文摘要

涡旋是流体动力流的标志。最近的研究表明,超纯导体中的强烈相互交互的电子可以显示出流体动力行为的特征,包括负非局部耐药性,狭窄通道中的Poiseuille流动以及违反Wiedemann-Franz定律。在这里,我们提供了电子流体中漩涡的首次可视化。通过利用纳米级扫描超导量量子干扰装置(鱿鱼端)上的量子干扰装置,我们会在通过小孔连接到相邻窄的窄电流携带带中的圆形腔室中的电流分布,并在高纯度II型型II型WEYL SEMIMIMETAL SEMIMITAL WTE2中。在此几何形状中,Gurzhi动量扩散长度和孔径的大小决定了涡旋稳定相图。我们发现涡旋仅用于小孔,而流量是层状(非涡流),用于较大的光圈,与对流体动力学状态的理论分析一致,与低温下WTE2中弹道传输的期望相反。此外,在涡流到范围的过渡附近,我们观察到腔室中的一个涡流分成两个涡流,这种行为只能在流体动力学方面发生,并且不能通过弹道传输来维持。这些发现表明了一种新型的流体动力流动机制:代替通常认为的电子电子散射在大量下,在低温下它变得极为弱,而是通过在薄纯晶体的平面表面上的小角度散射来实现电荷载体的空间扩散。这种表面诱导的para-hydrodnymics为探索和利用电子流动性电子系统中的电子流体提供了新的途径。

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.

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