Europhys. Lett.
Volume 68, Number 3, November 2004
Page(s) 440 - 446
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 16 October 2004
Europhys. Lett., 68 (3), pp. 440-446 (2004)
DOI: 10.1209/epl/i2004-10205-7

Optical and acoustic intersubband plasmons

M. Rösch1, E. Batke1, K. Köhler2 and P. Ganser2

1  Physikalisches Institut der Universität Würzburg, Am Hubland D-97074 Würzburg, Germany
2  Fraunhofer-Institut für Angewandte Festkörperphysik Tullastraße 72, D-79108 Freiburg, Germany

received 1 April 2004; accepted in final form 31 August 2004
published online 16 October 2004

Intersubband plasmon modes in a tunneling coupled bilayer system based on a 40 $\un{nm}$ wide $\chem{GaAs/Al_{0.3}Ga_{0.7}As}$ double heterostructure are studied by grating-coupler-assisted far-infrared spectroscopy. Both the charge density and the space symmetry of the bilayer can be tuned via front gate and are determined by means of magnetotransport measurements. We observe a strong-coupling behavior of the bilayer intersubband plasmon branches, resulting in the novel feature of optical and acoustic intersubband modes. The transmission spectra are excellently described by the self-consistently calculated absorption of the bilayer electron gas. Our theory in the framework of the current-response scheme takes into account the optics of the grating coupler and includes the interaction between the quasi-two-dimensional plasmon excitations.

71.45.Gm - Exchange, correlation, dielectric and magnetic response functions, plasmons.
73.20.Mf - Collective excitations (including excitons, polarons, plasmons and other charge-density excitations).
73.21.Fg - Quantum wells.

© EDP Sciences 2004