Quantum theory of time-dependent transport in graphene

Doktorsavhandling, 2017

High-quality ballistic electronic devices made from graphene are becoming an experimental reality. Carbon-based electronics is heralded if not to succeed or surpass then to complement the existing semiconducting technology. This thesis investigates graphene-based devices from a theoretical point of view with the focus on high-frequency applications, where the material is expected to have a large impact. We develop a quantum-mechanical description of time-dependent transport in mesoscopic graphene samples based on a scattering matrix approach similar to Landauer-Büttiker treatment of non-relativistic charge carriers. We investigate scattering processes involved in transport through a GFET and identify resonant mechanisms that lead to enhancement of the source-drain current under an oscillating gate signal. We propose a tunable selective frequency multiplication scheme and a radiation detector with operation relying on such mechanisms. The performance of the proposed devices is investigated in terms of their shot noise and Fano factor, which we show to be suppressed due to Klein tunnelling even for strong driving of the system. Finally, we apply the formalism to a quantum pump based on an asymmetric potential profile with respect to the gate electrode doping and compute the current through it, revealing that the temperature and the back gate bias can be used to switch the direction of the current.