在特殊情况下，材料中的载流子表现为粘性流体。在这项工作中，该研究团队通过扫描隧道电位仪研究了这种行为，以探测石墨烯中电子流体在通过由平滑且可调的面内p-n结势垒定义的通道时的纳米级流动。该研究团队还观察到，随着样品温度和通道宽度的增加，电子流体的流动经历了从弹道到粘性模式的克努森-古尔芝（Knudsen-to-Gurzhi）转变，其特征是通道电导超过弹道极限，并且抑制了电荷在势垒上的积累。相关结果通过二维粘性电流流动的有限元模拟得到了很好的建模，并且阐明了费米液体流动是如何随着载流子密度、通道宽度和温度的变化而演变的。
据悉，当电子-电子碰撞主导与缺陷和其他电阻源的碰撞时，导体中的电子流变得具有粘性。研究这种粘性的一种方法是物理上制造电子流过的狭窄通道，但这种通道的粗糙边缘使得与理论的比较变得棘手。
附：英文原文
Title: Imaging the breaking of electrostatic dams in graphene for ballistic and viscous fluids
Author: Zachary J. Krebs, Wyatt A. Behn, Songci Li, Keenan J. Smith, Kenji Watanabe, Takashi Taniguchi, Alex Levchenko, Victor W. Brar
Issue&Volume: 2023-02-17
Abstract: The charge carriers in a material can, under special circumstances, behave as a viscous fluid. In this work, we investigated such behavior by using scanning tunneling potentiometry to probe the nanometer-scale flow of electron fluids in graphene as they pass through channels defined by smooth and tunable in-plane p-n junction barriers. We observed that as the sample temperature and channel widths are increased, the electron fluid flow undergoes a Knudsen-to-Gurzhi transition from the ballistic to the viscous regime characterized by a channel conductance that exceeds the ballistic limit, as well as suppressed charge accumulation against the barriers. Our results are well modeled by finite element simulations of two-dimensional viscous current flow, and they illustrate how Fermi liquid flow evolves with carrier density, channel width, and temperature.
DOI: abm6073
Source: https://www.science.org/doi/10.1126/science.abm6073