Physics Department and Institute of Nanotechnology, Bar-Ilan University, Ramat Gan, 52900 Israel.
Synchrotron SOLEIL L'Orme des Merisiers, BP 48 Saint-Aubin, 91192 Gif-sur-Yvette, France.
Phys Rev Lett. 2019 Jan 18;122(2):023902. doi: 10.1103/PhysRevLett.122.023902.
We present the observation of peculiar nonmonotonic photon energy dependencies of the count rates and of the rocking curves of parametric down-conversion of x rays into ultraviolet far from any atomic resonances. The observations cannot be explained by models that consider only atomic or bond charge responses and suggest that collective phenomena contribute to the effect. We propose an interpretation that includes nonlinear interactions with plasmons, which can explain the existence of peaks in this energy range. Our Letter implies that nonlinear interactions between x rays and either ultraviolet or visible radiation can be utilized as a powerful atomic-scale probe for collective effects in solids.
我们观察到了一种特殊的非单调光子能量依赖性，这种依赖性存在于 x 射线的参量下转换为远紫外的光过程中的计数率和摇摆曲线中，而且这种依赖性在任何原子共振之外都存在。这些观察结果不能用仅考虑原子或键电荷响应的模型来解释，这表明集体现象对这种效应有贡献。我们提出了一种解释，其中包括与等离激元的非线性相互作用，这可以解释在这个能量范围内存在峰值的现象。我们的信暗示，x 射线与紫外或可见光之间的非线性相互作用可以被用作一种强大的原子尺度的探针，用于探测固体中的集体效应。
