Phonon Excitations of Composite Fermion Landau Levels

TL;DR

This paper investigates phonon excitations in fractional quantum Hall states, revealing Landau level transitions of Composite Fermions and a unique spin transition at filling factor 2/3 explained by partial polarization.

Contribution

It provides experimental evidence linking phonon excitations to Landau level transitions and proposes a new explanation for the spin transition at nu=2/3.

Findings

Phonon excitations correspond to Landau level transitions of Composite Fermions.

At nu=2/3, a linear field dependence suggests a spin transition.

Partial polarization explains the observed spin transition at nu=2/3.

Abstract

Phonon excitations of fractional quantum Hall states at filling factors nu = 1/3, 2/5, 4/7, 3/5, 4/3, and 5/3 are experimentally shown to be based on Landau level transitions of Composite Fermions. At filling factor nu = 2/3, however, a linear field dependence of the excitation energy in the high-field regime rather hints towards a spin transition excited by the phonons. We propose to explain this surprising observation by an only partially polarized 2/3-ground-state making the energetically lower lying spin transition also allowed for phonon excitations.