The Role of Substrate Roughness in Superfluid Film Flow Velocity
The Role of Substrate Roughness in Superfluid Film Flow Velocity
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基底粗糙度对超流膜流速的作用
DOI：
10.1007/s10909-018-02119-w
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发表时间：
2019
影响因子：
2
通讯作者：
Fukuyama Hiroshi
中科院分区：
文献类型：
--
作者：
Usami Jun;Kato Nobuyuki;Matsui Tomohiro;Fukuyama Hiroshi
众所周知，当容器壁被一薄层固体空气污染时，超流He的表观膜流率显著增加。然而，其微观机制尚未得到足够的澄清。我们在很大程度上不同的条件下测量了容器壁的表面积（0.77-6.15 μ m）和表面形态，使用烧结银细粉（粒度：0.10 μ m）和多孔玻璃（孔径：0.5，1 μ m）。与未经处理的光滑玻璃壁相比，我们可以增加两个数量级以上，其中液氦作为连续流而不是离散滴从容器底部流下。通过模拟表面形态，我们估计了容器的有效周长，并计算了流量，其中是表观周长，而不考虑微观表面结构。各种容器的结果js值在四个因子内是恒定的，这表明，的增强在如此巨大的程度上起着重要的作用，并且超流临界速度不会发生明显的变化。测量的j的温度依赖性表明，在我们的实验中的值是由施瓦茨的涡旋脱钉模型确定的（Phys Rev B 31（9）：5782，1985）。 https://doi.org/10.1103/PhysRevB.31.5782 具有几个nm尺寸的钉扎位点。
It is known that the apparent film flow rateof superfluidHe increases significantly when the container wall is contaminated by a thin layer of solid air. However, its microscopic mechanism has not yet been clarified enough. We have measuredunder largely different conditions for the container wall in terms of surface area (0.77–6.15 m) and surface morphology using sintered silver fine powders (particle size: 0.10m) and porous glass (pore size: 0.5, 1m). We could increaseby more than two orders of magnitude compared to non-treated smooth glass walls, where liquid helium flows down from the bottom of the container as a continuous stream rather than discrete drips. By modeling the surface morphology, we estimated the effective perimeter of the containerand calculated the flow rate, whereis the apparent perimeter without considering the microscopic surface structures. The resultantjvalues for the various containers are constant within a factor of four, suggesting that the enhancement ofplays a major role to changeto such a huge extent and that the superfluid critical velocity,, does not change appreciably. The measured temperature dependence ofjrevealed thatvalues in our experiments are determined by the vortex depinning model of Schwarz (Phys Rev B 31(9):5782, 1985. https://doi.org/10.1103/PhysRevB.31.5782 ) with several nm size pinning sites.