超短双电子脉冲的空间与能量关联
Spatial and energetic correlations of ultrashort two electron pulses
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中文总结 AI 辅助
本文表征了针尖处双电子脉冲的三维库仑关联，发现横向空间间距小的电子对存在3.3 eV能隙，结合光阑与能量滤波可将多电子脉冲抑制至g(2)=0.02，为相关研究及仪器设计提供基础。
中文摘要 AI 辅助
当两个电子从金属针尖在飞秒时间尺度下发射到纳米尺度体积中时，会产生强库仑关联。纵向关联表现为能量偏移，已在裸针尖和电子显微镜中被观测到，但横向关联几乎未被探索。本文首次完成了针尖处这类三维关联的完整实验表征，发现横向空间间距小的电子对存在宽度为3.3 eV的明显能隙，而纵向能量间距小的电子对则表现出强横向排斥，使它们的平均相互发散角显著增加34.5%。测量结果与半经典点粒子模拟高度吻合，模拟显示最大能隙幅度主要由激光脉冲持续时间决定，最大空间间距则由针尖半径决定。后者可用于生成亚泊松电子束的极为简单方法：大多数电子光学装置中已存在的光阑可作为电子数敏感滤波器，结合能量滤波后，在保留3%电子束的情况下，多电子脉冲的抑制达到前所未有的g(2)=0.02。这些结果为后续电子纠缠、关联电子显微镜研究及超快电子光学仪器设计奠定了基础。
英文摘要
When two electrons are emitted from a metallic needle tip into a nanometric volume on femtosecond timescales, strong Coulomb correlations arise. While longitudinal correlations, manifested as energy shifts, have been observed both from bare tips and in electron microscopes, transverse correlations remain hardly explored. Here, we present the first complete experimental characterization of such 3D correlations from needle tips. We find that electron pairs of small transversal spatial separation exhibit a pronounced energy gap of 3.3 eV width, while electrons of small longitudinal energy separation show strong transverse repulsion, increasing their average mutual divergence angle by a substantial 34.5%. The measurements are in excellent agreement with semiclassical point-particle simulations. These reveal that the maximal energy-gap magnitude is primarily determined by the laser pulse duration, whereas the maximal spatial separation is governed by the tip radius. The latter can be exploited in a remarkably simple method to generate strongly sub-Poissonian electron beams: A mere aperture, notably present in most electron-optical setups anyway, can act as an electron number sensitive filter. In combination with energy filtering we find an unprecedented suppression of multi-electron pulses reaching g(2) = 0.02 when keeping 3% of the electron beam. These results provide a foundation for future studies of electron entanglement, correlated electron microscopy, and the design of ultrafast electron-optical instruments.
