Engineered graphene Josephson junctions probed by quantum interference effects

After the introduction in Ch.1. the theoretical background of the investigated physical phenomena is given in Ch.2. In Ch.3 the fabrication of the nano structures is described and some of basic properties of graphene based Josephson junction with superconducting molybdenum-rhenium contacts are summarized. In the end of the chapter the applied methods for processing the data are explained. Afterwards the results of the supercurrent transport in superlattices of graphene and boron-nitride are summarized, which reveal the existence of van Hove singularities and satellite Dirac points in the band structure. In Ch.5 different realized approaches to create a helical quantum Hall state in graphene are described using the engineering of van der Waals heterostructures. The potential coupling of the helical states to superconductors was investigated. In the last experimental chapter, Ch.6, we focus on the magnetic field dependence of a double layer graphene heterostructure and show by current-phase relation measurements, that highly transparent superconducting modes exists within both graphene layers. In Ch.7 a summary of the thesis is given and possibilities of future experiments are sketched.