OPTICAL-ABSORPTION BY A LANDAU-QUANTIZED 2-DIMENSIONAL ELECTRON-GAS WITH ONE-DIMENSIONAL PERIODIC DELTA-MODULATION

An exact numerical diagonalization technique is used to calculate the energy eigenstates of a Landau-quantized two-dimensional electron gas under a one-dimensional periodic delta-modulation. On the basis of the se calculations, we develop a self-consistent field theory for the abs orption coefficient in the mid-infrared frequency regime. An extensive investigation is carried out in which we find that the plasmon mode c hanges from a cyclotron mode when the modulation is weak to tunnelling -split modes for the intermediate modulation and finally to edge and 1 D lattice magnetoplasmon modes when the modulation is strong. Our nume rical results show that as the magnetic field decreases, there exists electron tunnelling. However, for strong magnetic fields, electron tun nelling is suppressed. This suppression of electron tunnelling is sign alled by the crossover of two tunnelling-split modes into a cyclotron mode at strong magnetic fields. The eigenenergy of the edge mode oscil lates with electron density, related to soft or hard potential walls f rom the modulation for which the electron stays in extended and locali zed states, respectively.