Ballistic Graphene-based Dirac Devices

最近新一代高迁移率石墨烯样品的开发，使狄拉克费米子能够在许多微米的距离上进行弹道传播，这激发了人们对石墨烯中相干电荷输运和干涉现象的兴趣。由于弹道石墨烯中的载流子同时具有电子和波光学特性，这些新颖的实验能力，加上复杂的门控技术，为控制载流子流动和实现石墨烯中的狄拉克费米子的真正电子光学现象开辟了原理上的可能性。然而，尽管取得了这一惊人的进展，但对石墨烯中电子波传播的适当控制仍然有限。基于最近与该领域实验组的成功合作，我们建议研究弹道石墨烯器件中的各种电子光学现象，包括输运和干涉测量、引导、准直和捕获狄拉克费米子等方面。这特别包括以下相互关联的目标：我们将与Schönenberger小组（巴塞尔）合作，开发基于石墨烯的迈克尔逊和马赫-曾德干涉仪的第一个概念证明，并设计最佳几何形状，旨在基于石墨烯的电子干涉测量。作为石墨烯电子光学和干涉测量的先决条件，我们调用单极和双极石墨烯设置来实现电场和磁场控制的有效载流子引导。作为实现准直电子束的另一种方法，我们将进一步考虑p-n和p-n-p基石墨烯空腔，作为电子谐振器和发射器。我们将研究利用这种腔产生电荷载流子的高度定向发射的可能性，从而推广变形介观光学腔的光发射概念。为了定量理解和可靠预测这种电子光学效应，我们将采用先进的大规模石墨烯系统量子输运模拟，并结合现实的静电器件建模。

The recent development of a new generation of high-mobility graphene samples, enabling ballistic propagation of Dirac fermions over distances of many microns, has spurred an impressive renewal of interest in coherent charge transport and interference phenomena in graphene. Since carriers in ballistic graphene exhibit both electronic and wave-optical properties, these novel experimental abilities, together with sophisticated gating techniques, open up the principle possibility to control charge carrier flow and to put in reach true electron optics phenomena for Dirac fermions in graphene. Still, despite this stunning progress decent control of electron wave propagation in graphene is still limited. Building on recent successful cooperation with experimental groups in this field, we hence propose to investigate various electron-optics phenomena in ballistic graphene devices, including aspects of transport and interferometry, of guiding, collimating and trapping Dirac fermions. This includes in particular the following inter-related objectives: We will develop first proofs of concept and devise optimum geometries for graphene-based Michelson and Mach-Zehnder interferometers, in cooperation with the Schönenberger group (Basel), aiming at graphene-based electron interferometry. As one prerequisite of graphene electron optics and interferometry, we invoke uni- and bipolar graphene settings for electric and magnetic field-controlled efficient charge carrier guiding. As an alternative approach to achieve collimated electron beams, we will further consider p-n and p-n-p-based graphene cavities, acting as electron resonators and emitters. We will investigate the possibility to use such cavities to generate highly directional emission of charge carriers, thereby generalizing concepts for light emission from deformed mesoscopic optical cavities. For a quantitative understanding and reliable predictions of such electron-optics effects we will employ advanced quantum transport simulations for large-scale graphene systems, combined with realistic electrostatic device modelling.