We report experimental observation of an unexpectedly large thermopower in mesoscopic two-dimensional (2D) electron systems on GaAs/AlGaAs heterostructures at sub-Kelvin temperatures and zero magnetic field. Unlike conventional non-magnetic high-mobility 2D systems, the thermopower in our devices increases with decreasing temperature below 0.3 K, reaching values in excess of 100 μV/K, thus exceeding the free electron estimate by more than two orders of magnitude. With support from a parallel independent study of the local density of states, we suggest such a phenomenon to be linked to intrinsic localized states and many-body spin correlations in the system.
@article{arxiv.0906.0445,
title = {Highly enhanced thermopower in two-dimensional electron systems at milliKelvin temperatures},
author = {Srijit Goswami and Christoph Siegert and Matthias Baenninger and Arindam Ghosh and Michael Pepper and Ian Farrer and David A. Ritchie},
journal= {arXiv preprint arXiv:0906.0445},
year = {2015}
}