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Slippage of Helium Films

氦膜的滑移

基本信息

批准号：
11640340
负责人：
SUZUKI Masaru
金额：
$ 1.98万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11640340/
关键词：
Friction Slippage Physisorbed Film Helium ヘリウム吸着膜

项目摘要

Friction is a common force, but is poorly understood from a microscopic point of view. Recently, experimental observations of atomic-scale friction were reported using newly developed techniques, e.g., the atomic force microscope(AFM), and the quartz-crystal microbalance(QCM). And the peculiar friction nature has been observed in an atomic scale. Recently, Krim and her colleagues measured the mechanical response of noble-gas films on a noble-metal substrate at 77K using the QCM technique. On the other hand, One may expect that since the attraction force of helium atom is so weak, physisorbed helium films slide easily on a substrate.Thus motivated, we investigated the slippage of both superfluid and nonsuperfluid helium films on a two-dimensional porous material, hectrite. In the present experiments, the ultrasonic technique was adopted for the measurements of the mechanical response of these films. When the film slips, a rapid increase in sound velocity and an attenuation peak are observed.We found that nonsuperfluid helium films slip from the oscillating substrate under certain conditions. Up to the coverage at which the fluid state appears at absolute zero, nonsuperfluid ^3He and ^4He films slipped from the oscillation at low temperatures, and this slippage was inhibited as the coverage increases further. In addition, it was found that from the temperature dependence of the slippage, a thermally activated process plays an important role in the frictional force of this system.

摩擦力是一种常见的力，但从微观的角度来看，人们对它的理解很少。近年来，利用原子力显微镜（AFM）和石英晶体微天平（QCM）等新技术对原子尺度摩擦进行了实验观察。这种特殊的摩擦性质已经在原子尺度上被观察到。最近，Krim和她的同事们使用QCM技术测量了77K下贵金属衬底上稀有气体薄膜的机械响应。另一方面，人们可能会认为，由于氦原子的引力很弱，物理吸附的氦膜很容易在衬底上滑动。因此，我们研究了超流和非超流氦膜在二维多孔材料——锂离子锂上的滑移。在本实验中，采用超声波技术测量了这些薄膜的力学响应。当薄膜滑动时，声速迅速增加，并出现衰减峰。我们发现，在一定条件下，非超流氦膜会从振荡基底上滑落。在流体状态出现在绝对零度的覆盖范围内，非超流体^3He和^4He薄膜在低温下从振荡中滑动，并且随着覆盖范围的进一步增加，这种滑动被抑制。此外，从滑移的温度依赖性来看，热激活过程对该体系的摩擦力起着重要作用。