固体~（4-）He的低温剪切模量变化及其与超实性的关系
Low Temperature Shear Modulus Changes in Solid 4-He and Connection to Supersolidity
摘要：
超流性，即没有摩擦的液体流动，在氦中很常见。“超固体”的第一个证据，它在量子固体中的类似物，来自最近的扭转振荡器（TO）测量涉及4-He。在低于200 mK的温度下，TO频率增加，这表明一些固体与振荡器去耦。这种行为已经被几个小组复制，但固体4-He对压力差和持续电流没有反应，并且还没有看到其他超流的特征。实验和理论都表明，这是一种缺陷。这些也会影响固体的力学行为，因此我们测量了固体4-He在低频率和低应变下的剪切模量。我们观察到大的增加低于200 mK，具有相同的依赖于测量振幅，3-He杂质浓度和退火的去耦中看到TO实验。这种不寻常的弹性行为解释的位错网络，这是钉扎的3-He在最低温度，但变得移动100 mK以上。TO实验中的频率变化似乎与这些位错的运动有关，也许是通过破坏可能的超固态。
英文摘要：
Superfluidity, liquid flow without friction, is familiar in helium. The first evidence for "supersolidity", its analogue in quantum solids, came from recent torsional oscillator (TO) measurements involving 4-He. At temperatures below 200 mK, TO frequencies increased, suggesting that some of the solid decoupled from the oscillator. This behavior has been replicated by several groups but solid 4-He does not respond to pressure differences and persistent currents and other signatures of superflow have not been seen. Both experiments and theory indicate that defects are involved. These should also affect the solid's mechanical behavior and so we have measured the shear modulus of solid 4-He at low frequencies and strains. We observe large increases below 200 mK, with the same dependence on measurement amplitude, 3-He impurity concentration and annealing as the decoupling seen in TO experiments. This unusual elastic behavior is explained in terms of a dislocation network which is pinned by 3-He at the lowest temperatures but becomes mobile above 100 mK. The frequency changes in TO experiments appear to be related to the motion of these dislocations, perhaps by disrupting a possible supersolid state.
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