Fractional Quantum Hall Effect and Wigner Crystal of Two-Flux Composite Fermions

TL;DR

This study investigates the spin-polarization transitions of fractional quantum Hall states in GaAs quantum wells, revealing the formation of a ferromagnetic Wigner crystal of two-flux composite fermions near specific filling factors.

Contribution

It provides new insights into the spin transitions and the emergence of a ferromagnetic Wigner crystal of composite fermions in fractional quantum Hall systems.

Findings

Identification of spin-polarization transitions at ν=3/4 and 5/4.

Observation of reentrant integer quantum Hall effect following full spin polarization.

Linking the reentrant phase to a ferromagnetic Wigner crystal of composite fermions.

Abstract

In two-dimensional electron systems confined to GaAs quantum wells, as a function of either tilting the sample in magnetic field or increasing density, we observe multiple transitions of the fractional quantum Hall states (FQHSs) near filling factors $\nu=3/4$ and 5/4. The data reveal that these are spin-polarization transitions of interacting two-flux composite Fermions, which form their own FQHSs at these fillings. The fact that the reentrant integer quantum Hall effect near $\nu=4/5$ always develops following the transition to full spin polarization of the $\nu=4/5$ FQHS strongly links the reentrant phase to a pinned \emph{ferromagnetic} Wigner crystal of two-flux composite Fermions.