DC Transport In Multi-terminal Asymmetric Graphene Nanoribbon

Since the discovery of fullerenes, carbon-based materials have been the subject of intense research, led to the discovery of graphene—a two-dimensional (2D) allotrope of carbon. Among systems with only carbon atoms, graphene plays an important role since it is the basis to understand the electronic properties in other allotropes. To cut graphene sheet at certain direction with a pair of parallel lines, we will get graphene nanoribbons, which can be classified into two edges:zigzag and armchair edges. The graphene nanoribbons could be used as connections in nanodevices, so it is meaningful to make a study of their electronic transport properties. In this article we want to study the transport properties of multi-terminal asymmetric graphene nanoribbons.Here we mainly discuss a model of asymmetric T-shaped graphene nanoribbon (TGNR), where a semi-infinite zigzag graphene nanoribbon is connected to an infinite armchair graphene nanoribbon. This T-shaped junction is asymmetric to its vertical center line, thus the couplings between the intersection and the two horizontal nanoribbons are different. It is because of the different couplings leading to the particular transport properties of asymmetric TGNR, different from that of symmetric TGNR. For the electrons far away from Fermi energy, they transport from vertical ribbon to horizontal ribbons symmetrically; but for electrons near Fermi energy, their transport from vertical arm to horizontal arms is asymmetric. In this article we mainly discuss the properties of asymmetric transport, in the meantime we also discuss LDOS, and the effect of the width of graphene nanoribbons on the transport properties.