Intrinsic Gap of the nu=5/2 Fractional Quantum Hall State

TL;DR

This paper measures the excitation gap of the nu=5/2 fractional quantum Hall state at low magnetic fields, compares it with theoretical predictions, and discusses the role of disorder and Landau level mixing in understanding its intrinsic properties.

Contribution

It provides experimental measurements of the nu=5/2 gap at low fields and analyzes the discrepancy with theory, highlighting the importance of non-perturbative Landau level mixing.

Findings

Measured nu=5/2 gap as 262+/-15 mK at ~2.6 T

Large discrepancy between experimental intrinsic gap and theoretical predictions

Inclusion of non-perturbative Landau level mixing may be necessary

Abstract

The fractional quantum Hall effect is observed at low field, in a regime where the cyclotron energy is smaller than the Coulomb interaction. The nu=5/2 excitation gap is measured to be 262+/-15 mK at ~2.6 T, in good agreement with previous measurements performed on samples with similar mobility, but with electronic density larger by a factor of two. The role of disorder on the nu=5/2 gap is examined. Comparison between experiment and theory indicates that a large discrepancy remains for the intrinsic gap extrapolated from the infinite mobility (zero disorder) limit. In contrast, no such large discrepancy is found for the nu=1/3 Laughlin state. The observation of the nu=5/2 state in the low-field regime implies that inclusion of non-perturbative Landau level mixing may be necessary to better understand the energetics of half-filled fractional quantum hall liquids.