Quantum Hall effect in graphene: the role of the contacts and the device geometry

We investigate the motion of electronic wave-packets in the mean-field potential of a graphene Hall bar. The presence of Ohmic contacts enforces metallic boundary conditions along the source and drain contacts and affects the global form of the Hall potential in small devices, offering a possible explanation for the difficulty to detect the QHE in graphene in a four-terminal setup. Our injection-model of the QHE takes into account the existence of hot-spots in the device, which break any translational invariance. References: http://www.quantumdynamics.de/publications.html