Abstract:We propose numerical simulations of longitudinal magnetoconductance through a finite antidot lattice located inside an open quantum dot with a magnetic field applied perpendicular to the plane. The system is connected to reservoirs using quantum point contacts. We discuss the relationship between the longitudinal magnetoconductance and the generation of transversal couplings between the induced open quantum dots in the system. The system presents longitudinal magnetoconductance maps with crossovers ͑between tr… Show more
“…where the self-energies S R and Σ L of the contact leads are numerically calculated using the recursive Green function method [31,[33][34][35][36]. With these propagators we computed the DOS and the local density of states (LDOS) as described in [31,35,37].…”
We report the existence of two sub-lattices in metallic graphene nanoribbons that present a decoupled behavior. Each sub-lattice, one for extended states (ES) and another exclusively for localized states (LS), is formed by a combination of A and B graphene sites. In the sub-lattice ES all electronic transport phenomena occur, including the Klein tunneling through an external applied potential barrier. In contrast, the sub-lattice LS does not contribute to the transport of quasi-particles and strongly localized states are induced within the potential barrier region. The sub-lattices ES and LS are detected by analyzing Klein states and totally localized states that were systematically perturbed by the contributions of hyperboloid bands generated by the potential barrier. This is performed by gradually increasing the energy of the applied potential. The existence of both sub-lattices are tested by considering disorder and magnetic field effects in the system. The results indicate that both sublattices behave as if there are decoupled, even at the presence of an external applied barrier and that they can be coupled by applying an external magnetic field.
“…where the self-energies S R and Σ L of the contact leads are numerically calculated using the recursive Green function method [31,[33][34][35][36]. With these propagators we computed the DOS and the local density of states (LDOS) as described in [31,35,37].…”
We report the existence of two sub-lattices in metallic graphene nanoribbons that present a decoupled behavior. Each sub-lattice, one for extended states (ES) and another exclusively for localized states (LS), is formed by a combination of A and B graphene sites. In the sub-lattice ES all electronic transport phenomena occur, including the Klein tunneling through an external applied potential barrier. In contrast, the sub-lattice LS does not contribute to the transport of quasi-particles and strongly localized states are induced within the potential barrier region. The sub-lattices ES and LS are detected by analyzing Klein states and totally localized states that were systematically perturbed by the contributions of hyperboloid bands generated by the potential barrier. This is performed by gradually increasing the energy of the applied potential. The existence of both sub-lattices are tested by considering disorder and magnetic field effects in the system. The results indicate that both sublattices behave as if there are decoupled, even at the presence of an external applied barrier and that they can be coupled by applying an external magnetic field.
“…This will not be analyzed in this work, since we are interested in the low magnetic field limit for emulating a bona fide mesoscopic system, in which the host lattice effects are not important. Note that mesoscopic effects can modify the electronic structure associated with the tight binding host lattice [43]. This suggests that the results of the QW-OQD transition for both low energies (E < 20 meV) and magnetic fields (φ/φ 0 < 0.05) cannot be extrapolated to the high energy and magnetic field regimes.…”
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. We analyze the transition from a quantum wire to an open quantum dot and then to an effective closed system. The transition, as a function of w, occurs in the following sequence: evolution of quasi-Landau levels to Fano resonances and quasi-bound states between the quasi-Landau levels, followed by the formation of crossings that evolve to anti-crossings inside the quasi-Landau level region. After that, Fano resonances are created between the quasi-Landau states with the final generation of resonant tunneling peaks. By comparing the G(E,B) maps, we identify the closed and open-like limits of the system as a function of the applied magnetic field. These results were used to build quantum openness diagrams G(w,B). Also, these maps allow us to determine the w-limit value from which we can qualitatively relate the closed system properties to the open one. The above analysis can be used to identify single spinless particle effects in experimental measurements of the open quantum dot limit.
“…Assim, a matriz Tight Binding (para o caso 2D) deduzida a partir da equação de Schrödinger é uma matriz de blocos tridiagonais [7,22]. Nesta matriz, o bloco diagonal é formado pelas cadeias transversais e os blocos secundarios são as submatrizes que conectam longitudinalmente às cadeias transversais.…”
Section: Caso 2dunclassified
“…Na seção seguinte, partindo da equação de Schrödinger, equação (1), e utilizando-se de um procedimento de discretização, deduziremos a matriz Tight Binding mostrada na equação (2). Posteriormente faremos uma extensão deste procedimento e deduziremos a matriz Tight Binding para o caso 2D [7,22].…”
Resumo Neste trabalho realizamos a montagem de uma matriz hamiltoniana para um gás de elétrons bidimensional não interagente. Estes sistemas podem ser formados na interface de heteroestruturas do GaAs-AlGaAs e, na presença de potenciais de confinamento, serem usados como transistores quânticos. Partindo da equação de Schrödinger na aproximação da massa efetiva, deduzimos os Hamiltonianos 1D e 2D na base de sítios Tight Binding. Estes Hamiltonianos foram obtidos através do procedimento de discretização da equação de Schrödinger. Para o caso unidimensional, o resultado encontrado foi a conhecida matriz tridiagonal e, para o caso bidimensional, uma matriz de blocos tridiagonais. A discretização realizada permitiu a dedução dos valores das energias de sítio e de hopping do sistema estudado. Estes resultados demonstraram a ligação direta entre a equação de Schrödinger e o método Tight Binding, e, tais resultados, são muito úteis na realização de métodos numéricos, os quais não são abordados na literatura básica de Física do Estado Sólido.
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