Estudo dos efeitos da modulação da velocidade de Fermi na polarização dos vales no grafeno

Abstract

In this dissertation we will explore the properties of the valleys in graphene, since in graphene there are two pseudospins, one related to the sublattice and other related to the degree of freedom of the Dirac points and is called the pseudospin of the valley. As these valleys lie in the Dirac points located between the conduction and valence bands, the study of these valleys became a target for research. As the spintronics that uses the spin of the electron, the use of the to transport information gave rise to a new area of technology, the valleytronics. We the influence of a Fermi velocity modulation in the transmission and polarization of the valleys in a system characterized by a substrate which has the function of opening energy gap in the graphene monolayer that is on top of it, with metal plates juxtaposed in the graphene layer so that the Fermi velocity was modulated, an external magnetic field and an electrostatic potential, obtaining a Dirac Hamiltonian dependent on a potential vector, electrostatic potential and energy gap. We used the Dirac equation obtained to study the transmittance of the carriers, analyzing the possibility of adjusting the polarization in the valleys with the Fermi velocity modulation through a parameterization with the energy considering that the energy changes considerably with the Fermi velocity, with this we show that the system is able to confine electrons confirming some results of theoretical researches carried out with magnetic barriers, opposing the Klein tunneling. Our main result was to show that the Fermi velocity modulation can control the polarization of the valley, and it is possible to create valley filters in graphene.