Elastic effects in torsional oscillators containing solid helium
Elastic effects in torsional oscillators containing solid helium
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DOI：
10.1103/physrevb.85.180501
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发表时间：
2012-05
影响因子：
3.7
通讯作者：
J. Beamish;A. Fefferman;A. Haziot;X. Rojas;S. Balibar
中科院分区：
文献类型：
--
作者：
J. Beamish;A. Fefferman;A. Haziot;X. Rojas;S. Balibar
最近的一些实验使用扭转振子来研究固体氦的行为。当温度低于200 mK时，振荡器频率增加，这种效应归因于氦质量的一小部分解耦，这是“超固体”相的特征。然而，氦的剪切模量在200mk以下也会增加，扭转振荡器的频率取决于它的弹性特性，以及它的惯性。在许多实验中，氦气是通过扭转棒中的孔引入的，在那里它的剪切模量有助于杆的刚度。在具有较大扭转杆孔的振荡器中，氦气剪切模量的变化可以产生整个低温频移，这被解释为质量解耦。对于这些振子，我们还发现已知的扭转棒中氦的弹性特性可以解释观察到的TO振幅依赖性（已被解释为临界速度）和TO耗散峰。然而，在其他振荡器中，这些弹性效应很小，观察到的频率变化必须有不同的来源。
A number of recent experiments have used torsional oscillators to study the behavior of solid helium. The oscillator frequencies increased at temperatures below 200 mK, an effect attributed to decoupling of a fraction of the helium mass – the signature of a “supersolid” phase. However, helium’s shear modulus also increases below 200 mK and the frequency of a torsional oscillator depends on its elastic properties, as well as on its inertia. In many experiments helium is introduced via a hole in the torsion rod, where its shear modulus contributes to the stiffness of the rod. In oscillators with relatively large torsion rod holes, changes in the helium’s shear modulus could produce the entire low temperature frequency shifts that have been interpreted as mass decoupling. For these oscillators we also find that the known elastic properties of helium in the torsion rod can explain the observed TO amplitude dependence (which has been interpreted as a critical velocity) and the TO dissipation peak. However, in other oscillators these elastic effects are small and the observed frequency changes must have a different origin.