Multicomponent fractional quantum Hall states with subband and spin degrees of freedom

TL;DR

This paper investigates fractional quantum Hall states in wide GaAs quantum wells with two occupied subbands, revealing pseudospin polarization transitions influenced by spin and subband interactions, and providing a new measure of composite fermion energy separations.

Contribution

It demonstrates how Landau level crossings induce pseudospin transitions in fractional quantum Hall states, offering a novel quantitative approach to measure composite fermion energy level separations.

Findings

Pseudospin polarization transitions occur near Landau level crossings.

Energy level separations are smaller at higher spin polarization.

Transitions serve as a new measure of composite fermion energy differences.

Abstract

In wide GaAs quantum wells where two electric subbands are occupied we apply a parallel magnetic field or increase the electron density to cause a crossing of the two $N=0$ Landau levels of these subbands and with opposite spins. Near the crossing, the fractional quantum Hall states in the filling factor range $1<\nu<3$ exhibit a remarkable sequence of pseudospin polarization transitions resulting from the interplay between the spin and subband degrees of freedom. The field positions of the transitions yield a new and quantitative measure of the composite Fermions' discrete energy level separations. Surprisingly, the separations are smaller when the electrons have higher spin-polarization.