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

TL;DR

This study reports an unexpectedly large thermopower in mesoscopic 2D electron systems at very low temperatures, exceeding free electron estimates and likely linked to localized states and spin correlations.

Contribution

It presents the first experimental observation of giant thermopower in 2D electron systems at milliKelvin temperatures, highlighting the role of many-body effects.

Findings

Thermopower exceeds 100 μV/K below 0.3 K

Thermopower surpasses free electron estimates by over two orders of magnitude

Linked to localized states and spin correlations

Abstract

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.