Magnons and skyrmions in fractional Hall ferromagnets

TL;DR

This paper explains the differing temperature dependence of magnetization in quantum Hall ferromagnets at integer and fractional fillings by analyzing collective excitations, showing that particle-hole excitations dominate in fractional cases.

Contribution

It provides an analytic framework comparing magnon and particle-hole excitations, revealing their roles in magnetization behavior in fractional quantum Hall systems.

Findings

Interactions suppress magnetization at finite temperatures in fractional cases

Particle-hole excitations control magnetization at low temperatures in fractional systems

Magnons are less influential in fractional quantum Hall ferromagnets

Abstract

Recent experiments have established a qualitative difference between the magnetization temperature-dependences $M(T)$ of quantum Hall ferromagnets at integer and fractional filling factors. We explain this difference in terms of the relative energies of collective magnon and particle-hole excitations in the two cases. Analytic calculations for hard-core model systems are used to demonstrate that, in the fractional case, interactions suppress the magnetization at finite temperatures and that particle-hole excitations rather than long-wavelength magnons control $M(T)$ at low $T$.