Observation of new plasmons in the fractional quantum Hall effect: interplay of topological and nematic orders

TL;DR

This study uncovers new collective plasmon modes in the fractional quantum Hall regime, revealing complex interactions between topological order and nematic phases, and highlighting the robustness of the 5/2 superfluid state.

Contribution

It reports the first observation of intra-Landau-level plasmons in the second Landau level and their dependence on filling factors, providing new insights into quantum Hall and nematic phase interplay.

Findings

Detection of intra-Landau-level plasmons in the second Landau level.

Plasmon features indicate rotational symmetry breaking and translational invariance.

Suppression of plasmons at v=5/2 suggests dominance of paired superfluid state.

Abstract

Collective modes of exotic quantum fluids reveal underlying physical mechanisms responsible for emergent complex quantum ground states. We observe unexpected new collective modes in the fractional quantum Hall (FQH) regime: intra-Landau-level plasmons in the second Landau level measured by resonant inelastic light scattering. The plasmons herald rotational-symmetry-breaking phases in tilted magnetic fields and reveal long-range translational invariance in these phases. The fascinating dependence of plasmon features on filling factor provide new insights on interplays between topological quantum Hall order and nematic electronic liquid crystal phases. A marked intensity minimum in the plasmon spectrum at Landau level filling factor v = 5/2 strongly suggests that this paired state, which could support non-Abelian excitations, overwhelms competing nematic phases, unveiling the robustness of the 5/2 superfluid state for small tilt angles. At v = 7/3, a sharp and strong plasmon peak that links to emerging macroscopic coherence supports the proposed model of a FQH nematic state at this filling factor.