Quantized Dispersion of Two-Dimensional Magnetoplasmons Detected by Photoconductivity Spectroscopy

We find that the long-wavelength magnetoplasmon, resistively detected by photoconductivity spectroscopy in high-mobility two-dimensional electron systems, deviates from its well-known semiclassical nature as uncovered in conventional absorption experiments. A clear filling-factor dependent plateau-type dispersion is observed that reveals a so far unknown relation between the magnetoplasmon and the quantum Hall effect.

Figure 1

Schematic view of the sample structure and bias circuit showing a meandering long Hall bar with Ohmic contacts and a grating coupler.

Figure 2

FIR-PC spectra (solid curves) measured on sample M1218 around (a) $\nu =4$ and (b) $\nu =6$ in comparison with absorption spectra (dotted curves), displaying $\nu$-dependent variations of the magnetoplasmon energy detected in the PC spectra.

Figure 3

$B$-field dispersion of the CR and magnetoplasmons measured in sample M1218 by (a) absorption and (b) FIR-PC spectroscopy. In (a) the CR frequency is fit to the relation ${\omega }_c=eB/m^{*}$ (dashed line), and the magnetoplasmon frequency is fit either to Eq. (2) (solid curve) or by the hydrodynamical model (dotted curve). Theoretical curves in (b) are identical to that plotted in (a).

Figure 4

Filling-factor dependence of ${\Omega }_{mp}$ for the resistively detected magnetoplasmons measured in three different samples. The solid lines are the semiclassical predictions calculated using Eq. (3), which fit exactly to the dispersions measured by the absorption experiments.