We present thermopower S and resistance R measurements on GaAs-based mesoscopic two-dimensional electron gases (2DEGs) as functions of the electron density ns. At high ns we observe good agreement between the measured S and SMOTT, the Mott prediction for a non-interacting metal. As ns is lowered, we observe a crossover from Mott-like behaviour to that where S shows strong oscillations and even sign changes. Remarkably, there are absolutely no features in R corresponding to those in S. In fact, R is devoid of even any universal conductance fluctuations. A statistical analysis of the thermopower oscillations from two devices of dissimilar dimensions suggest a universal nature of the oscillations. We critically examine whether they can be mesoscopic fluctuations of the kind described by Lesovik and Khmelnitskii in Sov. Phys. JETP. \textbf{67}, 957 (1988).
@article{arxiv.1408.0730,
title = {Density-dependent thermopower oscillations in mesoscopic two-dimensional electron gases},
author = {Vijay Narayan and Eugene Kogan and Chris Ford and Michael Pepper and Moshe Kaveh and Jonathan Griffiths and Geb Jones and Harvey Beere and Dave Ritchie},
journal= {arXiv preprint arXiv:1408.0730},
year = {2015}
}