Figure 5: Electron density and Landau filling dependence of resonance parameters.
From: Microwave spectroscopy of the low-filling-factor bilayer electron solid in a wide quantum well
(a) The resonance peak conductivity, σpk, versus ν for many n successively offset by 20 μS. (b) The peak frequency fpk versus ν for the same n as (a) successively offset by 0.5 GHz. Spectra were taken at ν intervals of 0.005. We denote the lower and higher ν minima, respectively, by ν1 and ν2. (c) S/fpk versus n, where S is the integrated Re (σxx) versus f for the resonance, for ν=0.4 (where the integration is performed for 0.1<f<1.5 GHz). Conversion to γ is plotted on the top axis. The error in S/fpk is calculated as the difference between the measured value and that obtained by fitting the resonance to a Gaussian. The dotted line marks the theoretical value15 S/fpk=πe2ν/2h for full-charge carrier participation. Except near n=1.38, at which S/fpk is suppressed, the curve increases before saturating at ∼85% of the theoretical value. The observed increase in S/fpk demonstrates increase in the strength of the bilayer solid with increasing n as the available particles contribute to the solid. (d) The peak resonance σpk versus ν at fixed n=1.30. Here the well is imbalanced by asymmetric gating to transfer charge Δn between the two layers.
