We present the microscopic treatment of edge magnetoplasmons (EMPs) for the regime of not-too-low temperatures defined by the condition $\hbar \omega_{c}\gg k_{B}T\gg \hbar v_{g}/2\ell_{0}$, where $v_{g}$ is the group velocity of the edge states, $\ell_{0}=\sqrt{\hbar /m^{\ast}\omega_{c}}$ is the magnetic length and $\omega_{c}$ is the cyclotron frequency. We find a weakly damped symmetric mode, named helical edge magnetoplasmon, which is localized at the edge states region for filling factors $\nu =1, 2$ and \textit{very strong dissipation} $\eta_{T}=\xi /k_{x}\ell_{T}\agt\ln (1/k_{x}\ell_{T})\gg 1$, where the characteristic length $\ell_{T}=k_{B}T\ell_{0}^{2}/\hbar v_{g}\gg \ell_{0}/2$ with $\xi $ being the ratio of the local transverse conductivity to the local Hall conductivity at the edge states and $k_{x}$ is the wave vector along the edge; here other EMP modes are strongly damped. The spatial structure of the helical edge magnetoplasmon, transverse to the edge, is strongly modified as the wave propagates along the edge. In the regime of \textit{weak dissipation}, $\eta_{T}\ll 1$, we obtain exactly the damping of the fundamental mode as a function of $k_{x}$. For $\nu=4$ and weak dissipation we find that the fundamental modes of $n=0$ and $n=1$ Landau levels (LLs) are strongly renormalized due to the Coulomb coupling. Renormalization of all these EMPs coming from a metal gate and air half-space is studied.Comment: Copyright (2010) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Journal of Applied Physics 107, 104310 (2010) and may be found at http://link.aip.org/link/?JAP/107/104310.9 pages, 8 figure

The collapse of Hall gaps in the integer quantum Hall liquid in a quantum wire is investigated. Motivated by recent experiment [Pallecchi et al. PRB 65, 125303 (2002)] previous approaches are extended to treat confinement effects and the exchanged enhanced g factor in quantum wires. Two scenarios for the collapse of the ν = 1 state are discussed. In the first one the ν = 1 state becomes unstable at B (1) cr , due to the exchange interaction and correlation effects, coming from the edge-states screening. In the second scenario, a transition to the ν = 2 state occurs at B (2) cr , with a smaller effective channel width, caused by the redistribution of the charge density. This effect turns the Hartree interaction essential in calculating the total energy and changes B (2) cr drastically. In both scenarios, the exchange enhanced g-factor is suppressed for magnetic fields lower than Bcr. Phase diagrams for the Hall gap collapse are determined. The critical fields, activation energy, and optical g-factor obtained are compared with experiments. Within the accuracy of the available data, the first scenario is most probable to be realized.

A fitorremediação é uma técnica que utiliza plantas para remediar áreas contaminadas com metais pesados. Essa técnica possui grande vantagem devido à alta diversidade de vegetais que podem ser encontrados na natureza. Este trabalho teve como objetivo fazer o levantamento tecnológico dos métodos de fitorremediação usados na recuperação de ambientes impactados por metais pesados. A pesquisa foi realizada nos bancos de dados de patentes do Escritório Europeu de Patentes (Espacenet®) e do Instituto Nacional de Propriedade Industrial (INPI), utilizando as palavras-chave: remediação, planta, solo, metal pesado, recuperação e fitorremediação, e os códigos B09C1/00 e A01H5/00 da Classificação Internacional de Patentes. A China foi o destaque nesta pesquisa, apresentando os principais inventores e universidades detentoras de patentes, tendo o auge de depósito no ano de 2009. A técnica de fitorremediação mais utilizada foi a fitoextração. As tecnologias fitorremediadoras se mostram bastante promissoras para atender o mercado que é cada vez mais exigente e preocupado com os impactos ambientais.

At not-too-low temperatures, ħωc ≫ kBT ≫ ħvg/2ℓ0 where vg is the group velocity of the edge states and ℓ0 the magnetic length, we obtain new edge magnetoplasmons (EMPs). For ν = 1(2) and very strong dissipation, we find that all EMPs are very strongly damped, due to the dissipative processes at the edge states, but a new weakly damped mode termed edge helicon. We also study the effect of metallic gate on the helicon spectrum. For ν = 4 we obtain fundamental modes of the n = 0, 1 Landau levels and their renormalization due to the Coulomb coupling and the effect of a metallic gate on them.