Thermopower in the quantum Hall regime

TL;DR

This paper investigates how disorder affects thermopower in quantum Hall systems, revealing temperature-dependent behaviors and tunneling effects that align well with experimental observations.

Contribution

It introduces a model linking saddle point heights to filling factor deviations, explaining thermopower behavior in disordered quantum Hall samples.

Findings

Thermopower peaks increase as temperature decreases at high temperatures.

At lower temperatures, the thermopower maximum diminishes due to tunneling effects.

Model predictions agree with experimental conductance data near the minimum.

Abstract

We consider the effect of disorder on the themopower in quantum Hall systems. For a sample in the Corbino geometry, where dissipative currents are not carried by edge states, we find that thermopower behaves at high temperatures like a system with a gap and has a maximum which increases as the temperature is reduced. At lower temperatures this maximum reduces as a function of temperature as a result of tunneling across saddle points in the background potential. Our model assumes that the mean saddle point height varies linearly with the deviation in filling factor from the quantized value. We test this hypothesis against observations for the dissipative electrical conductance as a function of temperature and field and find good agreement with experiment around the minimum.