Low-temperature illumination and annealing of ultra-high quality quantum wells

TL;DR

This study explores how low-temperature illumination and annealing affect the fractional quantum Hall properties of ultra-high quality GaAs/AlGaAs quantum wells, leading to improved energy gaps and reproducible states.

Contribution

It introduces a novel illumination and annealing procedure that enhances FQH characteristics and achieves a significant energy gap for the 5/2 state.

Findings

Illumination reduces electron density by over an order of magnitude.

Annealing restores original density and improves FQH features.

Achieved a 600 mK energy gap for the 5/2 state.

Abstract

The effects of low temperature illumination and annealing on fractional quantum Hall (FQH) characteristics of a GaAs/AlGaAs quantum well are investigated. Illumination alone, below 1 K, decreases the density of the 2DEG electrons by more than an order of magnitude and resets the sample to a repeatable initial state. Subsequent thermal annealing at a few Kelvin restores the original density and dramatically improves FQH characteristics. A reliable illumination and annealing recipe is developed that yields an energy gap of 600 mK for the 5/2 state.