X-ray studies of low-temperature solid {sup 4}He.
X-ray studies of low-temperature solid {sup 4}He.
复制标题
低温固体 {sup 4}He 的 X 射线研究。
DOI：
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发表时间：
2008
期刊：
影响因子：
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通讯作者：
P. Platzman
中科院分区：
文献类型：
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作者：
C. Burns;N. Mulders;L. Lurio;M. Chan;A. Said;C. N. Kodituwakku;P. Platzman
最近的测量发现，固体{sup 4}He在T{约x}200MK处存在非经典转动惯量(NCRI)，从而推测这些材料中可能存在超固态。由于生长方法和热处理历史的不同，NCrI组分的差异表明缺陷在这一效应中起着重要的作用。利用X射线同步辐射，研究了固体{sup_4}He在50mK以下的晶体性质和缺陷性质。对峰强度和晶格参数的测量没有显示出超固态转变的迹象。使用与NCRI测量小组类似的生长方法，我们发现形成了大晶体(尺寸-毫米)。用小光束(低至10×10{Micro}m{sup 2})扫描，我们在这些晶体中分辨出与小角度晶界一致的马赛克结构。马赛克显示出随着时间的推移，即使在远离融化的温度下也会发生重大变化。我们讨论了这些缺陷与NCRI观测的相关性。
Recent measurements have found nonclassical rotational inertia (NCRI) in solid {sup 4}He starting at T{approx}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 {sup 4}He 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 (dimensions-millimeters) form. Scanning with a small (down to 10 x 10 {micro}m{sup 2}) beam, we resolve a mosaic structure within these crystals, which is consistent with 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.