Tunable diffusion of magnetic particles in a quasi-one-dimensional channel

The diffusion of a system of ferromagnetic dipoles confined in a quasi-one-dimensional parabolic trap is studied using Brownian dynamics simulations. We show that the dynamics of the system is tunable by an in-plane external homogeneous magnetic field. For a strong applied magnetic field, we find that the mobility of the system, the exponent of diffusion and the crossover time among different diffusion regimes can be tuned by the orientation of the magnetic field. For weak magnetic fields, the exponent of diffusion in the subdiffusive regime is independent of the orientation of the external field.Comment: 9 pages, 13 figures, to appear in Phys. Rev. E (2013

Bound vortex states and exotic lattices in multi-component Bose-Einstein condensates: The role of vortex-vortex interaction

We numerically study the vortex-vortex interaction in multi-component homogeneous Bose-Einstein condensates within the realm of the Gross-Pitaevskii theory. We provide strong evidences that pairwise vortex interaction captures the underlying mechanisms which determine the geometric configuration of the vortices, such as different lattices in many-vortex states, as well as the bound vortex states with two (dimer) or three (trimer) vortices. Specifically, we discuss and apply our theoretical approach to investigate intra- and inter-component vortex-vortex interactions in two- and three-component Bose-Einstein condensates, thereby shedding light on the formation of the exotic vortex configurations. These results correlate with current experimental efforts in multi-component Bose-Einstein condensates, and the understanding of the role of vortex interactions in multiband superconductors.Comment: Published in PR

Topological confinement in graphene bilayer quantum rings

We demonstrate the existence of localized electron and hole states in a ring-shaped potential kink in biased bilayer graphene. Within the continuum description, we show that for sharp potential steps the Dirac equation describing carrier states close to the K (or K') point of the first Brillouin zone can be solved analytically for a circular kink/anti-kink dot. The solutions exhibit interfacial states which exhibit Aharonov-Bohm oscillations as functions of the height of the potential step and/or the radius of the ring

Desempenho e número de avaliações necessárias à seleção de híbridos de coqueiro.

Objetivou-se avaliar o desempenho de seis híbridos de coqueiro e estimar o coeficiente de repetibilidade dos caracteres número de frutos/planta e produtividade de albúmen sólido, por diferentes procedimentos estatísticos. Utilizou-se o delineamento experimental de blocos casualizados, com seis repetições e parcelas representadas por 30 plantas em arranjo triangular eqüilátero de 8,5m. Considerando o desempenho dos híbridos durante nove anos para produção de frutos e de albúmen sólido, pode-se recomendar para plantio os híbridos PB 111, PB 113 e PB 141 nas condições do Estado do Pará, visando atender às indústrias (albúmen sólido) e também à venda de cocos ?in natura?. Os coeficientes de repetibilidade estimados pelos métodos Anova, componentes principais com base na covariância e na correlação e na análise da estrutura com base na correlação, foram 0,409, 0,655, 0,500 e 0,356 para número de frutos/planta, e de 0,573, 0,774, 0,655 e 0,554 para produtividade de albúmen sólido, respectivamente. Considerando o nível de 90% de predição como ótimo para a tomada de decisão sobre a superioridade relativa dos híbridos e tomando como base a estimativa de repetibilidade obtida pelo método de componentes principais (covariância), recomenda-se realizar somente cinco e três avaliações para número de frutos e produção de albúmen sólido, respectivamente.bitstream/item/48945/1/Boletim-PD-20-AMAZ-ORIENTAL.pd

Exciton trapping in magnetic wire structures

The lateral magnetic confinement of quasi two-dimensional excitons into wire like structures is studied. Spin effects are take into account and two different magnetic field profiles are considered, which experimentally can be created by the deposition of a ferromagnetic stripe on a semiconductor quantum well with magnetization parallel or perpendicular to the grown direction of the well. We find that it is possible to confine excitons into one-dimensional (1D) traps. We show that the dependence of the confinement energy on the exciton wave vector, which is related to its free direction of motion along the wire direction, is very small. Through the application of a background magnetic field it is possible to move the position of the trapping region towards the edge of the ferromagnetic stripe or even underneath the stripe. The exact position of this 1D exciton channel depends on the strength of the background magnetic field and on the magnetic polarisation direction of the ferromagnetic film.Comment: 10 pages, 7 figures, to be published in J. Phys: Condens. Matte