Coexistence of Composite-Bosons and Composite-Fermions in nu=1/2 + 1/2 Quantum Hall Bilayers

TL;DR

This paper explores the transition from composite fermion to composite boson states in bilayer quantum Hall systems at filling fraction near 1/2+1/2, proposing a coexistence scenario supported by wavefunction comparisons and transport theory.

Contribution

It introduces a novel coexistence model of composite bosons and fermions in quantum Hall bilayers, supported by trial wavefunctions and a compatible transport theory.

Findings

Wavefunction comparisons favor the coexistence scenario.

The proposed transport theory aligns with experimental observations.

The transition involves a gradual replacement of intra-layer with inter-layer correlations.

Abstract

In bilayer quantum Hall systems at filling fractions near nu=1/2+1/2, as the spacing d between the layers is continuously decreased, intra-layer correlations must be replaced by inter-layer correlations, and the composite fermion (CF) Fermi seas at large d must eventually be replaced by a composite boson (CB) condensate or "111 state" at small d. We propose a scenario where CBs and CFs coexist in two interpenetrating fluids in the transition. Trial wavefunctions describing these mixed CB-CF states compare very favorably with exact diagonalization results. A Chern-Simons transport theory is constructed that is compatible with experiment.