TY - JOUR
T1 - Excitonic effects in two-dimensional massless Dirac fermions
AU - Wang, Jianhui
AU - Fertig, H. A.
AU - Murthy, Ganpathy
AU - Brey, L.
PY - 2011/1/11
Y1 - 2011/1/11
N2 - 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.
AB - 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.
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U2 - 10.1103/PhysRevB.83.035404
DO - 10.1103/PhysRevB.83.035404
M3 - Article
AN - SCOPUS:79551642823
SN - 1098-0121
VL - 83
JO - Physical Review B - Condensed Matter and Materials Physics
JF - Physical Review B - Condensed Matter and Materials Physics
IS - 3
M1 - 035404
ER -