Ballistic Graphene-based Dirac Devices

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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.