Direct measurements of the fractional quantum Hall effect gaps

TL;DR

This study directly measures the energy gaps in the fractional quantum Hall effect in GaAs/AlGaAs systems, revealing linear magnetic field dependence and electron-hole symmetry, with correlated behaviors at specific spin transitions.

Contribution

It provides the first direct measurements of fractional quantum Hall gaps at low temperatures, highlighting their magnetic field dependence and symmetry properties.

Findings

Gap for nu=1/3 increases linearly with magnetic field

Nu=1/3 and nu=2/3 gaps are coincident in the fully spin-polarized regime

Correlated behavior observed at the nu=2/3 spin transition

Abstract

We measure the chemical potential jump across the fractional gap in the low-temperature limit in the two-dimensional electron system of GaAs/AlGaAs single heterojunctions. In the fully spin-polarized regime, the gap for filling factor nu=1/3 increases LINEARLY with magnetic field and is coincident with that for nu=2/3, reflecting the electron-hole symmetry in the spin-split Landau level. In low magnetic fields, at the ground-state spin transition for nu=2/3, a correlated behavior of the nu=1/3 and nu=2/3 gaps is observed.