Fractional Quantum Hall Effect of Composite Fermions

TL;DR

This paper reports the observation of fractional quantum Hall states at unconventional filling factors in a GaAs/AlGaAs quantum well, indicating residual interactions among composite fermions and providing insights into their spin polarization properties.

Contribution

It presents experimental evidence of FQHE at non-standard fractions, highlighting residual interactions among composite fermions and their spin polarization behavior.

Findings

Observation of FQHE at 4/11, 5/13, and other fractions.

Evidence of residual interactions among composite fermions.

The 4/11 state remains spin-polarized under tilt.

Abstract

In a GaAs/AlGaAs quantum well of electron density 1x10^{11} cm^{-2} we observe a fractional quantum Hall effect (FQHE) at filling factors nu=4/11, and 5/13, and weaker states at nu=6/17, 4/13, 5/17 and 7/11. These sequences of fractions do not fit into the standard series of integral quantum Hall effects (IQHE) of composite fermions (CF) at nu=p/(2mp +/- 1). They rather can be regarded as the FQHE of CFs attesting to residual interactions between these composite particles. In tilted magnetic fields the nu=4/11 state remains unchanged, strongly suggesting it to be spin-polarized. The weak nu=7/11 state vanishes quickly with tilt.