What Determines the Fermi Wave Vector of Composite Fermions?

TL;DR

This paper investigates the factors determining the Fermi wave vector of composite fermions near filling factor 1/2, revealing asymmetry and particle-hole symmetry breaking in their behavior.

Contribution

It demonstrates that the Fermi wave vector of composite fermions is set by minority carriers, challenging existing symmetric models near ν=1/2.

Findings

Asymmetry in commensurability resistance minima positions

Fermi wave vector linked to minority carriers

Evidence of particle-hole symmetry breaking

Abstract

Composite fermions (CFs), exotic particles formed by pairing an even number of flux quanta to each electron, provide a fascinating description of phenomena exhibited by interacting two-dimensional electrons at high magnetic fields. At and near Landau level filling $\nu=1/2$, CFs occupy a Fermi sea and exhibit commensurability effects when subjected to a periodic potential modulation. We observe a pronounced asymmetry in the magnetic field positions of the commensurability resistance minima of CFs with respect to the field at $\nu=1/2$. This unexpected asymmetry is quantitatively consistent with the CFs' Fermi wave vector being determined by the \textit{minority} carriers in the lowest Landau level. Our data indicate a breaking of the particle-hole symmetry for CFs near $\nu=1/2$.