Eur. Phys. J. B (2015) 88: 298
https://doi.org/10.1140/epjb/e2015-60467-8

Regular Article

Partial pseudospin polarization, latticetronics and Fano resonances in quantum dots based in graphene ribbons: a conductance spectroscopy

¹ Centro de Ciências Naturais e Humanas, Universidade Federal do ABC, 09210-170 Santo André, SP, Brazil
² Departamento de Física, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, SC, Brazil
³ Departamento de Ciências Exatas-EEIMVR, Universidade Federal Fluminense, 27255-125 Volta Redonda, RJ, Brazil

^a e-mail: lialfis@gmail.com

Received: 12 June 2015
Received in final form: 17 September 2015
Published online: 18 November 2015

Abstract

In this work we study, as a function of the height V and width L_b of the potential barriers, the transport of Dirac quasi-particles through quantum dots in graphene ribbons. We observed, as we increase V, a partial polarization (PP) of the pseudospin due to the participation of the hyperbolic bands. This generates polarizations in the sub-lattices A or B outside the dot regions for single, coupled, and open dots. Thus for energies around the Dirac point, the conductance G at both sides of the dot shows a latticetronics of conductances G_A and G_B as a function of V and L_b. This fact can be used as a PP spectroscopy which associates hole-type waves with the latticetronics. A periodic enhancement of PP is obtained with the increase of V in dots formed by barriers that completely occupy the nanoribbon width. For this case, a direct correspondence between G(V) and PP(V) exists. On the other hand, for the open dots, the PP(V) and the G(V) show a complex behavior that exhibit higher intensities when compared to the previous case. In the Dirac limit we have no backscattering signs, however when we move slightly away from this limit the first signs of confinement appear in the PP(V) (it freezes in a given sub-lattice). In the last case the backscattering fingerprints are obtained directly from the conductance (splittings). The open quantum dots are very sensible to their opening w_d and this generates Fano line-shapes of difficult interpretation around the Dirac point. The PP spectroscopy used here allows us to understand the influence of w_d in the relativistic analogues and to associate electron-type waves with the observed Fano line-shapes.