Physics – Condensed Matter – Mesoscale and Nanoscale Physics
Scientific paper
2002-04-04
Physics
Condensed Matter
Mesoscale and Nanoscale Physics
Revtex 4, 7 pages, 7 fugres
Scientific paper
Using simultaneous measurements of the attenuation and velocity of surface acoustic waves propagating along GaAs/Al$_{0.3}$Ga$_{0.7}$As heterostructures, complex ac conductance of the latters has been determined. In the magnetic fields corresponding to the middles of the Hall plateaus both the ac conductance, $\sigma (\omega)$, and the sheet electron density, $n_s$, in the two-dimensional conducting layer turn out to be dependent on the samples' cooling rate. As a result, the sample ``remembers'' the cooling conditions. The complex conductance is strongly dependent on an infrared illumination which also changes both $\sigma (\omega)$ and $n_s$. Remarkably, the correlation between $\sigma (\omega)$ and $n_s$ is \emph{universal}, i.e. it is independent of the way to change these quantities. The results are attributed to two-electron defects (so-called $DX^-$ centers) located in the Si doped layer.
Diakonov Andrey M.
Drichko Irina L.
Galperin Yu. M.
Preobrazenskii V. V.
Smirnov Ivan Yu.
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