Lateral tunneling, depopulation, and crossover effects on magnetoplasmons in multiwire superlattices

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Abstract
We derive the dispersion relation for magnetoplasmons in the random-phase approximation for a quantum-wire superlattice in the limit of strong lateral modulation and with a quantizing magnetic field B applied perpendicular to the plane of the system. We include lateral electron tunneling between adjacent quantum wires in the tight-binding approximation. Account is also taken of the dependence of the areal electron density and modulation strength on the varying gate voltage. We have also examined the role played by modulation strength (i.e., barrier height) and applied magnetic field on the collective modes. In this model, we study the crossover behavior of magnetoplasmons as the confinement varies continuously from the one-dimensional (1D) regime (strong modulation of the 2D electron gas) to the threshold of two-dimensional behavior where lateral electron tunneling becomes strong. We also study the single-particle properties such as the electron energy levels, Fermi energy, and level occupation number as functions of magnetic field, barrier height, and wire separation. Whenever there is a depopulation of a 1D Landau subband which can be produced by increasing the magnetic field or the gate voltage or by reducing the wire separation, there are abrupt changes in the slope of the Fermi-energy curve. This behavior is also obtained for the collective modes. Our model successfully reproduces several interesting features recently observed with use of far-infrared spectroscopy. Also, a commensurability relation between cyclotron orbits and umklapp scattering is predicted.