Valley transport in graphene-based devices: Achieving directionality and quantifying polarization

BERDAKIN, MATÍAS; BARRIOS VARGAS, JOSE EDUARDO ; FOA TORRES, LUIS E. F.

Dresden

Congreso; Graphene2018; 2018

First isolated in 2004 by Nobel Laureates Andre Geim and Konstantin Novoselov, graphene has united many record electrical, mechanical, thermal and optical properties (see for example [1]). The most notable electrical properties stem from its peculiar bandstructure which close to the Fermi energy combines a linear cone-like dispersion with pseudo-spin-momentum locking, similar to that expected for massless relativistic particles. There are two inequivalent cones in the energy dispersion, thereby leading to a binary spin-like flavor which is called the valley (see Fig.1). The valley degree of freedom can be exploited for useful functions and may replace charge in low power applications. A fundamental challenge is the formulation of a valley-controlled valley polarization source, in which the polarization of the valley degree of freedom can be flipped. This type of switchable valley source of electrons are the cornerstone for the future development of new valleytronics devices [2,3]. Here we explore the generation of charge and valley polarized unidirectional transport in graphene bilayers. With this aim we build on previous proposals [4,5] and show how one-way ambipolar charge and valley transport can be achieved in graphene bilayers under experimentally feasible conditions. Furthermore we analyze the valley polarization robusteness among the presence of valley scatterers in the system. We also analyze the persistence of valley polarization currents in other already known polarizers.