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Soft Magnetorotons and Broken-Symmetry States in Bilayer Quantum Hall Ferromagnets

Stefano Luin·Vittorio Pellegrini·Aron Pinczuk·Brian S. Dennis·Loren N. Pfeiffer·Ken W. West
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Abstract

The recent report on the observation of soft magnetorotons in the dispersion of charge-density excitations across the tunneling gap in coupled bilayers at total Landau level filling factor $ν_T=1$ is reviewed. The inelastic light scattering experiments take advantage of the breakdown of wave-vector conservation that occurs under resonant excitation. The results offer evidence that in the quantum Hall state there is a roton that softens and sharpens markedly when the phase boundary for transitions to highly-correlated compressible states is approached. These findings are interpreted with Hartree-Fock evaluations of the dynamic structure factor. The model includes the effect of disorder in the breakdown of wave-vector conservation and resonance enhancement profiles within a phenomenological approach. These results link the softening of magnetorotons to enhanced excitonic Coulomb interactions in the ferromagnetic bilayers.

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Stefano Luin, Vittorio Pellegrini, Aron Pinczuk, Brian S. Dennis, Loren N. Pfeiffer, Ken W. West. 2003-07-04. Soft Magnetorotons and Broken-Symmetry States in Bilayer Quantum Hall Ferromagnets. https://doi.org/10.1016/j.physe.2003.11.208

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