Abstract
The resistivity and thermopower of a double quantum well have been investigated in the temperature range as a function of voltage applied to a top gate. As in previous studies, the resistivity showed a strong resonance when the carrier densities in each well were approximately the same. In contrast, neither diffusion nor phonon-drag thermopower showed any sensitivity to the resonance. We have calculated the thermopower based on a model of two independent two-dimensional electron gases (2DEG’s) connected in parallel. In the case of phonon-drag thermopower, it was necessary to take into account the mutual screening of the electron-phonon interaction by electrons in each layer and also the local-field correction to the static dielectric function. We find that exhibits a dependence at low temperatures instead of the standard expected for single GaAs quantum wells. We also find that, for the lowest densities examined, the local-field correction enhances the magnitude of the calculated by over a factor of 2, in good agreement with experiment. As a check on the model of two independent 2DEG’s we have also calculated at resonance taking into account interwell coupling. The calculated values of so obtained are in good agreement with those obtained for uncoupled wells. This confirms the experimental result that is insensitive to the resonance condition.
- Received 12 November 2002
DOI:https://doi.org/10.1103/PhysRevB.67.155328
©2003 American Physical Society