Physics and Applications of Electron Vortex Beams

这项研究计划是关于在约克进行的新的调查，涉及最近发展的物理和应用，即电子涡旋（EV）束的受控产生。EV束是一种全新类型的电子束，与普通电子束不同的是，它们被赋予了一种扭曲（涡旋）性质，隐约类似于龙卷风涡旋。它们与光学涡旋（OVs）有相似之处，光学涡旋在过去二十年左右的时间里得到了大量的研究。OV已经在光镊和Spectrometer中找到应用，并且具有其他潜在的应用，例如在量子信息处理中。与OV和EV中的扭曲性质相关的是称为轨道角动量（OAM）的物理性质。然而，EV与OV的显著不同在于电子携带电荷和质量，并具有另一种称为自旋的内在扭曲性质，可以模糊地将其视为绕自身轴的旋转。此外，由于电子也具有波动性质，它们的波长比可见光的波长小得多。正是这一特征使它们在作为电动汽车的能力方面具有潜在的上级优势，能够在电子显微镜中拍摄比目前可能的更好的图像。也正是这种相同的性质使EV成为亚纳米级微小物质的优秀探针，并且EV通常被期望成为单个分子和原子水平的物质的优秀探针。电子自旋已被用于探测磁性材料的性质，但EV光束的轨道角动量含量呈现新的性质。电子相对于原子核的轨道运动对于理解原子和分子内的电子运动是至关重要的，但是直到最近，还没有被认为是通常与阴极射线管和电子显微镜中存在的电子束相关的性质。本提案旨在利用电动汽车的最新技术进步，探索这种电子束的广泛性质，并在基础研究和实际应用中进行调查。具体来说，我们将开发制造滤波器和转换器的方法，以在电子显微镜内产生各种EV光束，并研究它们在基础研究中的潜力以及为实际应用定制它们的方法。我们计划调查许多，到目前为止，与EV光束的轨道角运动之间的轨道角动量的量子化转移过程相关的未探索的现象，以探索材料的手性特定性质，例如磁性和等离子体跃迁。我们将探索电子涡旋现象驻留在光束内的相结构，以开发新的电子显微镜方法来揭示相结构，如生物分子。我们将利用有趣的“无衍射”效应的贝塞尔光束，即类贝塞尔窄光束，开发三维扫描显微镜断层扫描的纳米结构具有更好的分辨率。我们还将探索EV光束的复杂结构强度，以开发有效的原子捕获和纳米光刻工具。

This research proposal is about new investigations to be carried out at York concerned with the physics and applications of a very recent development, namely the controlled creation of electron vortex (EV) beams. EV beams are a brand new type of electron beams which differ from common electron beams in that they are endowed with a twisting (vortex) property vaguely akin to a tornado vortex. They bear resemblance to optical vortices (OVs), which have been much researched over the last two decades or so. OVs have found applications in optical tweezers and spanners and have other potential applications as, for example, in quantum information processing. Associated with the twisting property in both OVs and EVs is a physical property called orbital angular momentum (OAM). However, EVs differ significantly from OVs in that an electron carries electric charge and mass and possesses another intrinsic twisting property, called spin, which can be vaguely visualised as a rotation about its own axis. Furthermore, as electrons also possess wave properties, their wavelength is much smaller than that of visible light. It is this feature that makes them potentially superior in their ability as EVs to enable much better images in an electron microscope to be taken than currently possible. It is also this same property that makes an EV an excellent probe of tiny matter at the sub-nanoscale and EVs in general are expected to be excellent probes of matter at the individual molecular and atomic levels. The electron spin has been utilised in probing the properties of magnetic materials, but the orbital angular momentum content of EV beams presents new properties. The electron orbital motion relative to a nucleus has been vital in understanding the electronic motion within atoms and molecules, but, until recently, has not been considered to be a property normally associated with electron beams such as those existing inside cathode ray tubes and in electron microscopes. This proposal aims to take advantage of the recent technological advance of EVs to explore the extensive properties of such electron beams and to carry out investigations in both fundamental studies and practical applications. Specifically, we will develop ways to fabricate filters and convertors to generate various kinds of EV beams inside electron microscopes and to study their potential in fundamental research and ways of tailoring them for practical applications.We plan to investigate a number of many, as yet, unexplored phenomena associated with the processes of the quantized transfer of orbital angular momentum between the orbital angular motions of the EV beam and that of the sample to explore the chiral specific properties of materials, such as magnetic and plasmonic transitions. We will explore the phenomena of electron vortices residing in the phase structure within the beam to develop new electron microscopic methods for revealing phase structures such as biological molecules. We will exploit the interesting 'diffraction-free' effect of the Bessel beams, i.e. pencil-like narrow beams, to develop 3D scanning microscopy tomography of nanostructures with better resolutions. We will also explore the complex structured intensities of the EV beams to develop efficient atom trapping and nanolithographic tools.