利用等离激元干涉研究电子束相干性
Studying electron beam coherence using plasmon interference
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中文总结 AI 辅助
该研究通过离焦电子束激发氮化硅薄膜、单电子倏逝场激发等离激元散射体的实验验证了电子束相干性的相关预测，并提出可通过光与后选电子态关联恢复相干性的测量方案。
中文摘要 AI 辅助
高能电子与介电纳米结构、等离激元纳米结构相互作用时，会产生独特的阴极发光（CL）角分布，可为激发路径中的相干性提供重要信息。有一项反直觉的预测：由扩展电子波不同横向区域对应的激发所产生的CL信号互不相干、不会发生干涉，而在窄电子束的电磁场范围内，来自不同结构的信号则是相互相干的。我们通过研究离焦电子束激发氮化硅薄膜时的CL角发射轮廓，为上述效应提供了确凿的实验证据，实验结果表明该轮廓符合电子束斑内CL激发的非相干叠加规律。与之相反，当单个电子的倏逝场激发多个分离的等离激元散射体时，可观测到CL干涉现象。通过将发射光与后选择的电子态进行关联，相干性有望得以恢复，对此我们提出了一种可擦除电子轨迹路径信息的测量几何方案。
英文摘要
Energetic electrons create distinct cathodoluminescence (CL) angular distributions upon interaction with dielectric and plasmonic nanostructures, providing valuable information on coherences in the excitation pathways. A counterintuitive prediction is that the CL signals arising from the excitation associated with different lateral regions of an extended electron wave are mutually incoherent and do not interfere, while the signals originating from different structures within the electromagnetic field of a narrow electron beam are mutually coherent. We present conclusive experimental evidence of these effects by examining the angular CL emission profile from defocused electron-beam excitation of a thin silicon nitride film, which is shown to follow an incoherent sum of CL excitations within the electron beam spot. In contrast, CL interferences are observed for separated plasmonic scatterers excited within the evanescent field of a single electron. Coherence may be recovered through correlations between emitted light and post-selected electron states, for which we propose a measurement geometry that erases which-path information of the electron trajectory.
