固态氦的本征弹性行为和位错诱导弹性行为
Intrinsic and dislocation induced elastic behavior of solid helium
摘要：
最近的实验表明，固体4 He的剪切模量硬化在相同的温度范围内（低于200 mK），质量去耦和超固体已推断从扭转振荡器测量。这两种现象是明显相关的，晶体缺陷，特别是位错，似乎都参与其中。我们已经研究了退火的影响和固体4 He的弹性性能上施加大的应力的影响，使用声共振和直接的低频和低振幅的测量的剪切模量。退火和应力都会影响剪切模量，正如预期的那样，如果位错是负责的。然而，它是高温模量的影响;低温行为是不变的，似乎反映了固体氦的固有模量。我们解释这种行为的位错钉扎同位素3 He杂质在低温下，所以没有影响的剪切模量。在较高的温度下，它们变得流动并削弱固体。在低温下对晶体施加应力似乎会为位错网络引入新的缺陷或额外的钉扎位点，但这些效应可以通过将晶体加热到500 mK以上来逆转。这与晶体生长过程中产生的位错形成对比，位错仅在接近熔化的温度下退火。
英文摘要：
Recent experiments showed that the shear modulus of solid 4He stiffens in the same temperature range (below 200 mK) where mass decoupling and supersolidity have been inferred from torsional oscillator measurements. The two phenomena are clearly related and crystal defects, particularly dislocations, appear to be involved in both. We have studied the effects of annealing and the effects of applying large stresses on the elastic properties of solid 4He, using both acoustic resonances and direct low-frequency and low-amplitude measurements of the shear modulus. Both annealing and stressing affect the shear modulus, as expected if dislocations are responsible. However, it is the high temperature modulus which is affected; the low temperature behavior is unchanged and appears to reflect the intrinsic modulus of solid helium. We interpret this behavior in terms of dislocations which are pinned by isotopic 3He impurities at low temperatures and so have no effect on the shear modulus. At higher temperatures they become mobile and weaken the solid. Stressing the crystal at low temperatures appears to introduce new defects or additional pinning sites for the dislocation network but these effects can be reversed by heating the crystal above 500 mK. This is in contrast to dislocations produced during crystal growth, which are only annealed at temperatures close to melting.
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