Estados snake e filtros de vale baseados somente em tensão mecânica em monocamadas de grafeno

Abstract

Graphene exhibits several interesting electronic properties that make it a decisive material for the development of future devices. One of them is the existence of two (Dirac) valleys in its electronic spectrum, which enables the possibility of designing valley-tronic devices. Besides, graphene also exhibits great mechanical properties, being the thinnest material known to date and, still, the strongest yet measured. Its flexibility is a fascinating property, that makes it resist high mechanical stress. Moreover, it has been demonstrated that strain fields in graphene can be mapped into pseudo-magnetic fields for electrons in the layer. Thus, this allows us to use high strain fields to tune electronic properties of this material and, thereby, expand its set of possible technological applications. In this dissertation, the electronic transport along the direction parallel to a pseudo-magnetic barrier, induced by a non-uniform strain in a monolayer graphene nanoribbon, is theoretically investigated. In the region where the pseudo-magnetic field changes sign, we observe snake states, composed by semi-orbits with a single propagation direction, as expected for the analogous case of such a barrier induced by an ordinary external magnetic field. However, pseudo-magnetic fields point towards opposite directions in K and K’ valleys, which yields valley polarized snake states currents. Throughout this work, we discuss how to maximize the valley-filtering effect based on such a polarization, by adjusting the parameters defining the strain distribution along the graphene nanoribbon.