Unequal Layer Densities in Bilayer Wigner Crystal at High Magnetic Field

TL;DR

This study investigates how layer density imbalance affects the pinning mode resonances of bilayer Wigner crystals under high magnetic fields, revealing the persistence of interlayer coherence at moderate imbalances.

Contribution

It provides new insights into the behavior of bilayer Wigner crystals with unequal densities, especially regarding the survival of quantum interlayer coherence.

Findings

Two resonances for large d/a ratios with unequal densities.

Single resonance persists at small d/a despite density imbalance.

Interlayer coherence survives at moderate density imbalance.

Abstract

We report studies of pinning mode resonances of magnetic field induced bilayer Wigner crystals of bilayer hole samples with negligible interlayer tunneling and different interlayer separations d, in states with varying layer densities, including unequal layer densities. With unequal layer densities, samples with large d relative to the in-plane carrier-carrier spacing a, two pinning resonances are present, one for each layer. For small d/a samples, a single resonance is observed even with significant density imbalance. These samples, at balance, were shown to exhibit an enhanced pinning mode frequency [Zhihai Wang et al., Phys. Rev. Lett. 136804 (2007)], which was ascribed to a one-component, pseudospin ferromagnetic Wigner solid. The evolution of the resonance frequency and line width indicates the quantum interlayer coherence survives at moderate density imbalance, but disappears when imbalance is sufficiently large.