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arXiv 1504.01518cond-mat.mtrl-scicond-mat.other
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运动固体~ 4 He表面的表征

Characterization of the Surface of Moving solid 4He

Ethan Livne, Anna Eyal, Ori Scaly, Emil Polturak

摘要:

固体$^4$的晶粒即使嵌入固体内部,他也可以彼此相对移动。在这项工作中,我们描述了一个宏观运动的固体六方晶系$^4$ He组成的这种颗粒。通过对安装在扭转振荡器上的环形通道内的固体施加外部扭矩来引起运动。为了表征移动固体的表面,我们开发了一种使用嵌入在通道壁中的灵敏的“麦克风”的原位流动检测方法。运动是通过计算由一排排He原子移动经过麦克风引起的振动来检测的。这样的振动只在T=0.5K,我们的最低温度下被检测到。在这个温度下,在我们的精度范围内,与固体He相关的测量耗散为零。我们的结果表明,运动固体表面的取向是六方晶系结构的(0001)基面。在T=0.5 K时,我们发现,对于< 7微米/秒的速度,固体流动没有可检测到的摩擦。

英文摘要:

Crystal grains of solid $^4$He can move in relation to each other even when embedded inside the solid. In this work, we characterize a macroscopic motion of solid hcp $^4$He composed of such grains. Motion is induced by applying an external torque to the solid contained inside an annular channel mounted on a torsional oscillator. In order to characterize the surface of the moving solid, we developed an in-situ flow detection method using a sensitive "microphone" embedded in the wall of the channel. Motion is detected by counting the vibrations induced by rows of He atoms moving past the microphone. Such vibrations were detected only at T=0.5K, our lowest temperature. At this temperature, the measured dissipation associated with the solid He is zero within our accuracy. Our results indicate that the orientation of the surface of the moving solid is the (0001) basal plane of the hcp structure. At T=0.5 K, we found that for speeds < 7 micrometer/sec, the solid flows without detectable friction.

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