Physics and Applications of Electron Vortex Beams

这项研究建议是关于将在约克开展的与一项最新发展的物理和应用有关的新研究，即电子涡旋(EV)束的受控产生。EV电子束是一种全新的电子束，它与普通电子束的不同之处在于它具有类似于龙卷风涡旋的扭转(涡旋)特性。它们与光学涡旋(OV)有相似之处，在过去20年左右的时间里，光学涡旋得到了大量研究。OVS已经在光学镊子和扳手中找到了应用，并有其他潜在的应用，例如，在量子信息处理中。与OVS和EVS中的扭曲特性相关的是一种称为轨道角动量(OAM)的物理特性。然而，EVS与OVS的显著不同之处在于，电子携带电荷和质量，并具有另一种固有的扭曲性质，称为自旋，这可以模糊地想象为围绕自己的轴旋转。此外，由于电子也具有波的性质，它们的波长比可见光的波长小得多。正是这一特征使它们作为电动汽车的能力具有潜在的优势，能够在电子显微镜中拍摄到比目前可能的更好的图像。也正是这种相同的性质，使电动汽车成为亚纳米尺度上极好的微小物质探测器，而电动汽车一般被认为是在单个分子和原子水平上的优秀物质探测器。电子自旋已被用于探索磁性材料的性质，但EV束的轨道角动量含量呈现出新的性质。电子轨道相对于原子核的运动对于理解原子和分子内的电子运动是至关重要的，但直到最近，还没有被认为是通常与电子束有关的属性，例如存在于阴极射线管和电子显微镜中的电子束。这项建议旨在利用电动汽车最近的技术进步，探索这种电子束的广泛性质，并在基础研究和实际应用两方面进行研究。具体地说，我们将开发制造滤光器和转换器的方法来在电子显微镜中产生各种类型的EV束，并研究它们在基础研究中的潜力和为实际应用量身定做的方法。我们计划研究许多与EV束的轨道角运动和样品的轨道角运动之间的轨道角动量量化转移相关的许多尚未探索的现象，以探索材料的手性特殊性质，如磁性和等离子体跃迁。我们将探索电子涡旋驻留在电子束内的相结构中的现象，以开发新的电子显微镜方法来揭示生物分子等相结构。我们将利用贝塞尔光束有趣的无衍射效应，即铅笔状的窄光束，开发分辨率更高的纳米结构的3D扫描显微镜层析成像。我们还将探索EV光束的复杂结构强度，以开发高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.