Low-field diffusion magneto-thermopower of a high mobility two-dimensional electron gas

TL;DR

This study measures the low-field diffusion thermopower in a high mobility GaAs 2DEG, revealing Landau level oscillations and a large Nernst-Ettinghausen effect consistent with theory.

Contribution

It provides the first direct measurement of both longitudinal and transverse thermopower in a high mobility 2DEG at low magnetic fields, confirming theoretical predictions.

Findings

Landau level oscillations observed in thermopower

Syx is approximately 120 times larger than Sxx at 1 T

Experimental results agree with theoretical models

Abstract

The low magnetic field diffusion thermopower of a high mobility GaAs-heterostructure has been measured directly on an electrostatically defined micron-scale Hall-bar structure at low temperature (T = 1.6 K) in the low magnetic field regime (B < 1.2 T) where delocalized quantum Hall states do not influence the measurements. The sample design allowed the determination of the field dependence of the thermopower both parallel and perpendicular to the temperature gradient, denoted respectively by Sxx (longitudinal thermopower) and Syx (Nernst-Ettinghausen coefficient). The experimental data show clear oscillations in Sxx and Syx due to the formation of Landau levels for 0.3 T < B < 1.2 T and reveal that Syx is approximately 120 times larger than Sxx at a magnetic field of 1 T, which agrees well with the theoretical prediction.