Observation of collapse of pseudospin order in bilayer quantum Hall ferromagnets

TL;DR

This paper reports the observation of a collapse in pseudospin order in bilayer quantum Hall ferromagnets, revealing a new correlated state and anomalies in spin excitations under certain conditions.

Contribution

It demonstrates the breakdown of the full pseudospin ferromagnetic order at large tunneling gaps, introducing a novel correlated quantum Hall state at filling factor 1.

Findings

Reduced pseudospin order at large tunneling gaps

Emergence of a new correlated quantum Hall state

Anomalies in spin excitations with in-plane magnetic fields

Abstract

The Hartree-Fock paradigm of bilayer quantum Hall states with finite tunneling at filling factor $\nu$=1 has full pseudospin ferromagnetic order with all the electrons in the lowest symmetric Landau level. Inelastic light scattering measurements of low energy spin excitations reveal major departures from the paradigm at relatively large tunneling gaps. The results indicate the emergence of a novel correlated quantum Hall state at $\nu$=1 characterized by reduced pseudospin order. Marked anomalies occur in spin excitations when pseudospin polarization collapses by application of in-plane magnetic fields.