  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.
