Publications by authors named "Michel Mendoza"

We discretize the Schrödinger equation in the approximation of the effective mass for the two-dimensional electron gas of GaAs, without magnetic field and on the other hand, with magnetic field. This discretization leads naturally to Tight Binding (TB) Hamiltonians in the approximation of the effective mass. An analysis of this discretization allows us to gain insight into the role of site and hopping energies, which allows us to model the TB Hamiltonian assembly with spin: Zeeman and spin-orbit coupling effects, especially the case Rashba.

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We show here that potential barriers, applied to armchair nanoribbons, induce a hexagonal effective lattice, polarized in pseudospin on the sides of the barriers system, which has an effective unit cell greater than that of infinite graphene (pseudospin superstructure). This superstructure is better defined with the increase of the barrier potential, until a transport gap is generated. The superstructure, as well as the induced gap, are fingerprints of Kekulé distortion in graphene, so here we report an analogous effect in nanoribbons.

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The cloaking effect of electronic states was only reported in bilayer graphene. Here in this work we show that this effect can also be induced in armchair graphene nanoribbons (AGNRs), by potential barriers that modulate the chirality property of the system (correlation between pseudospins). These barriers manipulate the chirality and generates pseudospin polarizations on the sides of the barrier, which leaves spatial regions in evidence, in which states behave differently.

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In this work we study some applications for pseudo-spin filters. The filters are potential barriers with hyperboloid sub-band contributions that are locally applied over graphene nano-ribbons. These filters modulate the pseudo-spin and the quirality of the wave-function allowing the recovery of the conductance loss due to imperfections, bends, or constrictions (asymmetries) found in the system.

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We found that with an increase of the potential barrier applied to metallic graphene ribbons, the Klein tunneling current decreases until it is totally destroyed and the pseudo-spin polarization increases until it reaches its maximum value when the current is zero. This inverse relation disfavors the generation of polarized currents in a sub-lattice. In this work we discuss the pseudo-spin control (polarization and inversion) of the Klein tunneling currents, as well as the optimization of these polarized currents in a sub-lattice, using potential barriers in metallic graphene ribbons.

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We present quantum magneto-conductance simulations, at the quantum low energy condition, to study the open quantum dot limit. The longitudinal conductance G(E,B) of spinless and non-interacting electrons is mapped as a function of the magnetic field B and the energy E of the electrons. The quantum dot linked to the semi-infinite leads is tuned by quantum point contacts of variable width w.

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