Second Landau Level Fractional Quantum Hall Effects in the Corbino Geometry

TL;DR

This paper reports the fabrication and measurement of a Corbino-geometry device in ultra-high mobility GaAs heterostructures, enabling bulk transport studies of second Landau level fractional quantum Hall states without edge effects.

Contribution

It introduces a Corbino device for probing bulk properties of fractional quantum Hall states, especially the 5/2 state, using thermodynamic measurements.

Findings

Activation energy gaps for fractional quantum Hall states measured.

Edge effects are effectively ruled out in the measurements.

Activated transport in the second Landau level remains poorly understood.

Abstract

For certain measurements, the Corbino geometry has a distinct advantage over the Hall and van der Pauw geometries, in that it provides a direct probe of the bulk 2DEG without complications due to edge effects. This may be important in enabling detection of the non-Abelian entropy of the 5/2 fractional quantum Hall state via bulk thermodynamic measurements. We report the successful fabrication and measurement of a Corbino-geometry sample in an ultra-high mobility GaAs heterostructure, with a focus on transport in the second and higher Landau levels. In particular, we report activation energy gaps of fractional quantum Hall states, with all edge effects ruled out, and extrapolate the conductivity prefactor from the Arrhenius fits. Our results show that activated transport in the second Landau level remains poorly understood. The development of this Corbino device opens the possibility to study the bulk of the 5/2 state using techniques not possible in other geometries.