Bilayer quantum Hall ferromagnet in a periodic potential

Jianmin Sun, Ganpathy Murthy, H. A. Fertig, Noah Bray-Ali

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


The bilayer quantum Hall system at a total filling of νT =1 has long resisted explanation in terms of a true counterflow superfluid, though many experimental features can be seen to be "almost" that of a superfluid. It is widely believed that quenched disorder is the root cause of this puzzle. Here we model the nonperturbative effects of disorder by investigating the ν=1 bilayer in a strong periodic potential. Our model assumes that fermions are gapped and real spins are fully polarized, and concentrates on the pseudospin variable (the layer index), with the external potential coupling to the topological (Pontryagin) density of the pseudospin. We find that as the potential strength increases, there are ground-state transitions in which the topological content of the pseudospin configuration changes. These transitions are generically weakly first order with a new quadratically dispersing mode (in addition to the linearly dispersing Goldstone mode) sometimes becoming nearly gapless near the transition. We show that this leads to strong suppressions of both the Kosterlitz-Thouless transition temperature and the interlayer tunneling strength, which we treat perturbatively. We discuss how these results might extend to the case of true disorder.

Original languageEnglish
Article number195314
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number19
StatePublished - May 13 2010

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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