Elementary excitations in tunnel-coupled electron bilayers

A new class of single-particle excitations in tunnel-coupled electron bilayers is investigated by inelastic light scattering. The dispersion law and the dependence of the energies of these excitations on the degree of unbalance between the layers have been measured. A new spectroscopic method is proposed for determining the degree of unbalance between bilayers. (C) 2003 MAIK "Nauka/Interperiodica"

Collective excitations in double quantum wells with strong tunnel coupling

Spectra of collective and magnetic excitations in symmetric double quantum wells with strong tunnel coupling were studied by inelastic scattering. Gaps in the spectrum of collective and single-particle excitations associated with tunnel interwell splitting were measured. New excitation modes, namely, tunnel Bernstein modes, were detected in a magnetic field. Based on the dispersion and magnetic-field dependences of the energies of inelastic light scattering lines, a classification of excitations and magnetic excitations was given. (C) 2004 MAIK "Nauka / Interperiodica"

Intersubband collective excitations in a quasi-two-dimensional electron system in external magnetic field

The spectrum of collective excitations in a quasi-two- dimensional electron system was studied by the method of Raman scattering spectroscopy. In an applied magnetic field, such systems exhibit collective excitations related to the electron transitions between dimensionally quantized subbands with a change in the Landau level index (intersubband Bernstein modes). It is shown that these modes interact with the fundamental intersubband excitations of the charge and spin densities, the interaction energy being determined by the excitation quasimomentum. Interaction of the intersubband Bernstein modes and the fundamental intersubband excitations with quasi-two-dimensional LO phonons was studied. Behavior of the new branches of collective excitations in a quasi-two- dimensional electron system possessing more than one occupied Landau level was studied and the nature of these branches was determined. (C) 2002 MAIK "Nauka / Interperiodica"

Dimensional magnetoplasma resonance of 2D holes in (001) GaAs/AlGaAs quantum wells

Dimensional magnetoplasma resonance is observed and studied in a spatially confined, two-dimensional hole system in (001) GaAs/AlGaAs single quantum wells. From the analysis of the field dependence of the magnetoplasma resonance on the diameter of the 2D system, the semiclassical cyclotron hole mass is determined. Its value is found to be equal to 0.26m 0 (m 0 is the free electron mass), which considerably exceeds the theoretically predicted value. A method is proposed for a direct determination of the concentration and mobility of 2D holes from the analysis of the magnetoplasma resonance