Plasmon and magnetoplasmon excitation in two-dimensional electron space-charge layers on GaAs

Abstract

The excitation of two-dimensional (2D) plasmons in ${\mathrm{Al}}_{\mathrm{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathrm{x}}$As-GaAs heterostructures has been investigated with far-infrared transmission spectroscopy. Grating couplers of high efficiency and samples of high mobility (μ≊1.8×${10}^5$ ${\mathrm{cm}}^2$/V? make it possible to study the 2D plasmon dispersion up to plasmon wave vectors q≳2×${10}^5$ ${\mathrm{cm}}^{\mathrm{-}1}$. Thus we can test the theoretically predicted second-order q corrections to the dispersion due to nonlocal effects, finite thickness of the space-charge layer, and correlations. In perpendicular magnetic fields, a strong nonlocal interaction of the 2D magnetoplasmon resonance with harmonics of the cyclotron resonance n${\omega }_c$ (n=2,3,4,. . .) is observed. Excellent agreement is found with predictions of a classical nonlocal theory.