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Intra-Landau-level magnetoexcitons and the transition between quantum Hall states in undoped bilayer graphene

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Article number115455
<mark>Journal publication date</mark>29/03/2011
<mark>Journal</mark>Physical Review B
Issue number11
Number of pages6
<mark>Original language</mark>English


We study the collective modes of the quantum Hall states in undoped bilayer graphene in a strong perpendicular magnetic and electric field. Both for the well-known ferromagnetic state that is relevant for small electric field E-perpendicular to and the analogous layer polarized one suitable for large E-perpendicular to, the low-energy physics is dominated by magnetoexcitons with zero angular momentum that are even combinations of excitons that conserve Landau orbitals. We identify a long-wavelength instability in both states, and argue that there is an intermediate range of the electric field E-c((1)) < E-perpendicular to < E-c((s)) where a gapless phase interpolates between the incompressible quantum Hall states. The experimental relevance of this crossover via a gapless state is discussed.

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©2011 American Physical Society