Hole magnetoplasmons in quantum dots.

Abstract

For electrons in quantum dots the dipole absorption spectrum is known to reflect only magnetoplasmon modes with a rigid center-of-mass motion (``generalized Kohn's theorem''). A more complex behavior is expected for holes in quantum dots, as the valence-band mixing prohibits the separation of relative and center-of-mass coordinates, and the dipole field couples then also to the relative motion. We investigate theoretically the far-infrared response of hole-confining quantum dots, assuming a structure that can be realized by the lateral modulation of a two-dimensional hole gas in a ${\mathrm{Ga}}_{\mathit{x}}$${\mathrm{Al}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As-GaAs quantum well or heterojunction. The ground state of the many-hole system is determined in the local density approximation, using the 4\ifmmode\times\else\texttimes\fi{}4 Luttinger Hamiltonian to include the valence-band mixing. The collective response to a dipole field is calculated within the random phase approximation. The resulting far-infrared absorption spectra exhibit a rich set of dipole active magnetoplasmon modes with internal motions of the charge density, which due to the generalized Kohn's theorem are not possible for electrons in quantum dots. \textcopyright{} 1996 The American Physical Society.