Highly enhanced thermopower in two-dimensional electron systems at milliKelvin temperatures

Srijit Goswami, Christoph Siegert, Matthias Baenninger, Arindam Ghosh, Michael Pepper, Ian Farrer, David A. Ritchie

Published 2009-06-02Version 1

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 $\mu$V/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.