Improved Composite-Boson Theory of Monolayer and Bilayer Quantum Hall Ferromagnets

TL;DR

This paper develops an improved composite-boson theoretical framework for monolayer and bilayer quantum Hall ferromagnets, focusing on skyrmion excitations and their stability influenced by interlayer density differences.

Contribution

It introduces a refined composite-boson approach that accurately describes physical degrees of freedom and skyrmion excitations in quantum Hall ferromagnets, enhancing understanding of their stability.

Findings

Skyrmions are confined to the lowest Landau level.

Bilayer QH states become more stable with increased interlayer density difference.

The theory provides a better description of excitations in quantum Hall systems.

Abstract

An improved composite-boson theory of quantum Hall ferromagnets is formulated both for the monolayer and bilayer systems. In this scheme the field operator describes solely the physical degrees of freedom representing the deviation from the ground state. Skyrmions are charged excitations confined to the lowest Landau level. By evaluating the excitation energy of one skyrmion in the interlayer-coherent phase it is shown that the bilayer QH state becomes stabler as the interlayer density difference becomes larger.