Diffusion Thermopower of Quantum Hall States Measured in Corbino Geometry

TL;DR

This study measures the diffusion thermopower in a quantum Hall system using a Corbino geometry, revealing oscillations and sign reversals consistent with theoretical predictions involving disorder effects.

Contribution

It provides the first experimental measurement of diffusion thermopower in a Corbino quantum Hall setup, confirming theoretical models that include disorder effects.

Findings

Radial thermovoltages show sawtooth oscillations with magnetic field.

Sign reversals occur at the center of quantum Hall plateaus.

Results agree with self-consistent Born approximation theory.

Abstract

We have measured the diffusion thermopower of a quantum Hall system in a Corbino setup. A concentric electron-temperature gradient is introduced by irradiating microwaves, via a coplanar waveguide, near the outer rim of a circular mesa of a two-dimensional electron gas. The resulting radial thermovoltages exhibit sawtooth-like oscillations with the magnetic field, taking large positive (negative) values just below (above) integer fillings with sign reversal at the center of the quantum Hall plateaus. The behavior is in agreement with a recent theory [Y. Barlas and K. Yang: Phys. Rev. B 85 (2012) 195107], which treats disorder within the self-consistent Born approximation.