BCC与HCP -晶体对称性对固体$^4$ He高温迁移率的影响
BCC vs. HCP - The Effect of Crystal Symmetry on the High Temperature Mobility of Solid $^4$He
摘要：
本文报道了固体$^4$ He在1 K以上的扭振子（TO）实验结果。我们以前已经发现，单晶，一旦无序，显示出一定的流动性（去耦质量），即使在这些相当高的温度。单晶的去耦质量分数通常为20- 30%。在目前的工作中，我们进行了类似的测量多晶固体样品。多晶体的去耦质量要小得多，$\sim$ 1%，与其他小组观察到的相似。特别是，我们比较了与TO的旋转轴在不同的方向相对于重力生长的样品的属性。我们发现体心立方样品的退耦质量分数与旋转轴与重力的夹角无关。相比之下，当旋转轴和重力之间的角度在0和85度之间变化时，hcp样品显示出解耦质量分数的显著差异。固体中的位错动力学为这种各向异性提供了一种可能的解释。
英文摘要：
We report results of torsional oscillator (TO) experiments on solid $^4$He at temperatures above 1K. We have previously found that single crystals, once disordered, show some mobility (decoupled mass) even at these rather high temperatures. The decoupled mass fraction with single crystals is typically 20- 30%. In the present work we performed similar measurements on polycrystalline solid samples. The decoupled mass with polycrystals is much smaller, $\sim$ 1%, similar to what is observed by other groups. In particular, we compared the properties of samples grown with the TO's rotation axis at different orientations with respect to gravity. We found that the decoupled mass fraction of bcc samples is independent of the angle between the rotation axis and gravity. In contrast, hcp samples showed a significant difference in the fraction of decoupled mass as the angle between the rotation axis and gravity was varied between zero and 85 degrees. Dislocation dynamics in the solid offers one possible explanation of this anisotropy.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
