具有缺陷表层的晶体中的深度相关有序、双长度标度现象和交叉行为
Depth-dependent ordering, two-length-scale phenomena and crossover behavior in a crystal featuring a skin-layer with defects
摘要：
晶体中的结构缺陷是导致“双长度尺度”行为的原因，其中在临界漫射X射线散射中，尖锐的中心峰叠加在宽峰上。我们以前测量的标度行为的中心峰的散射从近表面区域的V2H晶体，其中有一个一级过渡的散装。随着温度向临界温度降低，可以看到临界行为的交叉，其中最接近临界点的温度范围由平均场指数表征。在过渡区附近，观察到一个小的两相共存区。转变温度和交叉温度的值随深度衰减。这些实验结果的解释是在这里提出的理论，其中刃位错在近表面区域中发生在壁在两个方向上垂直于表面取向的装置。由位错线引起的应变导致晶体中的有序化以大致圆柱形区域的生长发生。在区域达到一定大小后，临界行为发生交叉，平均场行为占主导地位。在更低的温度下，圆柱形区域之间的其余材料通过弱的一级跃迁有序化。
英文摘要：
Structural defects in a crystal are responsible for the "two length-scale" behavior, in which a sharp central peak is superimposed over a broad peak in critical diffuse X-ray scattering. We have previously measured the scaling behavior of the central peak by scattering from a near-surface region of a V2H crystal, which has a first-order transition in the bulk. As the temperature is lowered toward the critical temperature, a crossover in critical behavior is seen, with the temperature range nearest to the critical point being characterized by mean field exponents. Near the transition, a small two-phase coexistence region is observed. The values of transition and crossover temperatures decay with depth. An explanation of these experimental results is here proposed by means of a theory in which edge dislocations in the near-surface region occur in walls oriented in the two directions normal to the surface. The strain caused by the dislocation lines causes the ordering in the crystal to occur as growth of roughly cylindrically shaped regions. After the regions have reached a certain size, the crossover in the critical behavior occurs, and mean field behavior prevails. At a still lower temperature, the rest of the material between the cylindrical regions orders via a weak first-order transition.
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