Excitonic effects in two-dimensional massless Dirac fermions

Jianhui Wang, H. A. Fertig, Ganpathy Murthy, L. Brey

Research output: Contribution to journalArticlepeer-review

24 Scopus citations


We study excitonic effects in two-dimensional massless Dirac fermions with Coulomb interactions by solving the ladder approximation to the Bethe-Salpeter equation. It is found that the general four-leg vertex has a power-law behavior with the exponent going from real to complex as the coupling constant is increased. This change of behavior is manifested in the antisymmetric response, which displays power-law behavior at small wave vectors reminiscent of a critical state, and a change in this power law from real to complex that is accompanied by poles in the response function for finite-size systems, suggesting a phase transition for strong enough interactions. The density-density response is also calculated, for which no critical behavior is found. We demonstrate that exciton correlations enhance the cusp in the irreducible polarizability at 2kF, leading to a strong increase in the amplitude of Friedel oscillations around a charged impurity.

Original languageEnglish
Article number035404
JournalPhysical Review B - Condensed Matter and Materials Physics
Issue number3
StatePublished - Jan 11 2011

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics


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