Random-phase Approximation Treatment Of Edge Magnetoplasmons: Edge-state Screening And Nonlocality

A random-phase approximation (RPA) treatment of edge magnetoplasmons (EMP) is presented for strong magnetic fields, low temperatures, and integer filling factors \nu. It is valid for negligible dissipation and lateral confining potentials smooth on the scale of the magnetic length \ell_{0} but sufficiently steep that the Landau-level (LL) flattening can be neglected. LL coupling, screening by edge states, and nonlocal contributions to the current density are taken into account. In addition to the fundamental mode with typical dispersion relation \omega\sim q_x \ln(q_{x}), fundamental modes with {\it acoustic} dispersion relation \omega\sim q_x are obtained for \nu>2. For \nu=1,2 a {\bf dipole} mode exists, with dispersion relation \omega\sim q_x^3, that is directly related to nonlocal responses.Comment: Text 12 pages in Latex/Revtex format, 4 Postscript figure

Repulsion of Single-well Fundamental Edge Magnetoplasmons in Double Quantum Wells

A {\it microscopic} treatment of fundamental edge magnetoplasmons (EMPs) along the edge of a double quantum well (DQW) is presented for strong magnetic fields, low temperatures, and total filling factor \nu=2. It is valid for lateral confining potentials that Landau level (LL) flattening can be neglected. The cyclotron and Zeeman energies are assumed larger than the DQW energy splitting \sqrt{\Delta^2 +4T^2}, where \Delta is the splitting of the isolated wells and T the tunneling matrix element. %hen calculated unperturbed density profile is sharp at the edge. Using a random-phase approximation (RPA), which includes local and nonlocal contributions to the current density, it is shown that for negligible tunnel coupling 2T << \Delta the inter-well Coulomb coupling leads to two DQW fundamental EMPs which are strongly renormalized in comparison with the decoupled, single-well fundamental EMP. These DQW modes can be modified further upon varying the inter-well distance d, along the z axis, and/or the separation of the wells' edges \Delta y along the y axis. The charge profile of the {\it fast} and {\it slow} DQW mode varies, respectively, in an {\it acoustic} and {\it optical} manner along the y axis and is not smooth on the \ell_{0} scale. For strong tunneling \Delta\alt 2T these DQW modes are essentially modified when \Delta is changed by applying a transverse electric field to the DQW.Comment: Text 18 pages in Latex/Revtex/Preprint format, 2 Postscript figure

Surface electromagnetic modes in layered conductors in a magnetic field

A transfer-matrix approach is developed for studies of the collective electromagnetic modes in a semi-infinite layered conductor subjected to a quantizing external magnetic field perpendicular to the layers. The dispersion relations for the surface and bulk modes are derived. It is shown that the surface mode has a gap in the long-wavelength limit and exists only if the absolute value of the in-plane wave vector q exceeds the threshold value q*=−1/(a ln|Δ|). Depending on the sign of the parameter Δ=(ε−ε₀)/(ε₀+ε), the frequency of the surface mode ωs(q,Δ) goes either above (for Δ>0) or below (for Δ0 and Δ<0 (a is the interlayer separation; ε0 and ε stand for the dielectric constants of the media outside the sample and between the layers; q and k are the components of the wave vector in the plane and perpendicular to the layers, respectively)