固体~ 4 He从mK到熔化的结构和缺陷的X射线研究
X-ray Studies of Structure and Defects in Solid 4He from 50 mK to Melting
摘要：
最近的测量发现固体4 He在T ~ 200 mK开始具有非经典转动惯量（NCRI），导致推测这些材料中可能存在超固态。由于生长方法和退火历史的NCRI分数的差异意味着缺陷在效果中起重要作用。利用X射线同步辐射，我们研究了温度低至50 mK时固体~ 4 He中晶体的性质和缺陷的性质。峰值强度和晶格参数的测量没有显示超固态转变的迹象。使用类似于测量NCRI的那些组的生长方法，我们发现形成大晶体。用一个小的（低至10 × 10 μ m2）光束扫描，我们解决了这些晶体内的马赛克结构与许多小角度晶界一致。即使在远离融化的温度下，马赛克也显示出随着时间的推移而发生的重大变化。我们讨论这些缺陷的NCRI意见的相关性。
英文摘要：
Recent measurements have found non-classical rotational inertia (NCRI) in solid 4He starting at T ~ 200 mK, leading to speculation that a supersolid state may exist in these materials. Differences in the NCRI fraction due to the growth method and annealing history imply that defects play an important role in the effect. Using x-ray synchrotron radiation, we have studied the nature of the crystals and the properties of the defects in solid 4He at temperatures down to 50 mK. Measurements of peak intensities and lattice parameters do not show indications of the supersolid transition. Using growth methods similar to those of groups measuring the NCRI we find that large crystals form. Scanning with a small (down to 10 x 10 um2) beam, we resolve a mosaic structure within these crystals consistent with numerous small angle grain boundaries. The mosaic shows significant shifts over time even at temperatures far from melting. We discuss the relevance of these defects to the NCRI observations.
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