Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy
Transient lensing from a photoemitted electron gas imaged by ultrafast electron microscopy
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DOI：
10.1038/s41467-020-16746-z
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发表时间：
2020-01
影响因子：
16.6
通讯作者：
O. Zandi;Allan E. Sykes;Ryan D. Cornelius;Francis M. Alcorn;B. Zerbe;P. Duxbury;B. Reed;R. M. van der Veen
中科院分区：
文献类型：
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作者：
O. Zandi;Allan E. Sykes;Ryan D. Cornelius;Francis M. Alcorn;B. Zerbe;P. Duxbury;B. Reed;R. M. van der Veen
理解和控制超快电荷载流子动力学在（量子）科学和技术的不同领域具有根本的重要性。在这里，我们创造了一个三维的热电子气通过双光子光电子发射从铜表面在真空中。我们使用超快电子显微镜记录皮秒-纳秒时间尺度上的后续电子动力学的电影。在一个提示库仑爆炸后，随后的动力学的特点是由一个快速的扁圆形到扁长形的电子气体的形状转换，和周期性和长寿命的电子回旋振荡内的磁场的物镜透镜。在这种情况下，振荡电子的集体行为会导致瞬态的平均场透镜效应和图像中的明显失真。我们推导出随时间变化的电子气体透镜的焦距的解析表达式，并进行数值电子动力学和探针图像模拟，以确定库仑自场和图像电荷的作用。这项工作激发了二维电子气材料内部回旋动力学的可视化，并能够阐明电子/等离子体动力学和特性，这可能有利于高亮度电子和X射线源的发展。
Understanding and controlling ultrafast charge carrier dynamics is of fundamental importance in diverse fields of (quantum) science and technology. Here, we create a three-dimensional hot electron gas through two-photon photoemission from a copper surface in vacuum. We employ an ultrafast electron microscope to record movies of the subsequent electron dynamics on the picosecond-nanosecond time scale. After a prompt Coulomb explosion, the subsequent dynamics is characterized by a rapid oblate-to-prolate shape transformation of the electron gas, and periodic and long-lived electron cyclotron oscillations inside the magnetic field of the objective lens. In this regime, the collective behavior of the oscillating electrons causes a transient, mean-field lensing effect and pronounced distortions in the images. We derive an analytical expression for the time-dependent focal length of the electron-gas lens, and perform numerical electron dynamics and probe image simulations to determine the role of Coulomb self-fields and image charges. This work inspires the visualization of cyclotron dynamics inside two-dimensional electron-gas materials and enables the elucidation of electron/plasma dynamics and properties that could benefit the development of high-brightness electron and X-ray sources.