Composite Fermions with Tunable Fermi Contour Anisotropy

TL;DR

This paper demonstrates how a parallel magnetic field can significantly distort the Fermi contour of composite fermions in a high-quality two-dimensional hole system, revealing tunable anisotropy in their Fermi surface.

Contribution

It provides experimental evidence of tunable Fermi contour anisotropy of composite fermions using a parallel magnetic field in a 2D hole system.

Findings

Parallel magnetic field distorts the composite fermion Fermi contour

Fermi surface anisotropy is tunable via magnetic field strength

High-quality GaAs quantum well enables precise measurements

Abstract

The composite fermion formalism elegantly describes some of the most fascinating behaviours of interacting two-dimensional carriers at low temperatures and in strong perpendicular magnetic fields. In this framework, carriers minimize their energy by attaching two flux quanta and forming new quasi-particles, the so-called composite fermions. Thanks to the flux attachment, when a Landau level is half-filled, the composite fermions feel a vanishing effective magnetic field and possess a Fermi surface with a well-defined Fermi contour. Our measurements in a high-quality two-dimensional hole system confined to a GaAs quantum well demonstrate that a parallel magnetic field can significantly distort the hole-flux composite fermion Fermi contour.