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arXiv · 1408.0730

Density-dependent thermopower oscillations in mesoscopic two-dimensional electron gases

Vijay Narayan·Eugene Kogan·Chris Ford·Michael Pepper·Moshe Kaveh·Jonathan Griffiths·Geb Jones·Harvey Beere·Dave Ritchie
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Abstract

We present thermopower $S$ and resistance $R$ measurements on GaAs-based mesoscopic two-dimensional electron gases (2DEGs) as functions of the electron density $n_s$. At high $n_s$ we observe good agreement between the measured $S$ and $S_{\rm{MOTT}}$, the Mott prediction for a non-interacting metal. As $n_s$ 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).

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Vijay Narayan, Eugene Kogan, Chris Ford, Michael Pepper, Moshe Kaveh, Jonathan Griffiths, Geb Jones, Harvey Beere, Dave Ritchie. 2014-08-04. Density-dependent thermopower oscillations in mesoscopic two-dimensional electron gases. https://doi.org/10.1088/1367-2630/16/8/085009

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