Composite Fermions with a Warped Fermi Contour

TL;DR

This study investigates how the shape of the Fermi contour of composite fermions in a GaAs quantum well is affected by the Landau level origin, revealing warping influenced by the hole band characteristics.

Contribution

It provides the first direct measurement showing the Fermi contour warping of composite fermions depends on the Landau level from which they originate.

Findings

Composite fermions exhibit a warped Fermi contour when originating from a warped hole band.

The Fermi contour shape is strongly influenced by the Landau level characteristics.

Measurements demonstrate the impact of band warping on composite fermion properties.

Abstract

Via measurements of commensurability features near Landau filling factor $\nu=1/2$, we probe the shape of the Fermi contour for hole-flux composite fermions confined to a wide GaAs quantum well. The data reveal that the composite fermions are strongly influenced by the characteristics of the Landau level in which they are formed. In particular, their Fermi contour is $\textit{warped}$ when their Landau level originates from a hole band with significant warping.