1305.6334 (G. Gazzola et al.)

Arbitrary Parameters and Charge Conservation Constraints on the A.C.
Conductivity of Coulomb Interacting Massless Dirac Particles in Graphene    [PDF]

G. Gazzola, A. L. Cherchiglia, L. A. Cabral, M. C. Nemes, Marcos Sampaio

Using an invariant regularization independent framework to avoid spurious evaluation of arbitrary parameters we compute the a.c. conductivity correction C for Coulomb interacting massless Dirac particles in graphene in the collisionless limit (\omega >>T) using the polarization tensor approach. In order to remove arbitrarinesses introduced by regularization dependent free parameters of the model, we exploit two constraints to the amplitudes namely transversality of the polarization tensor and a Ward-Takahashi-like identity involving the vertex function and the electron self energy, both stemming from charge conservation. It turns out that while the transversality of the polarization tensor determines C=(19-6\pi)/12, the Ward-Takahashi-like identity involving the vertex function and the electron self energy yields C=(25-6\pi)/12. We compare our results to previous calculations in the literature.

View original: http://arxiv.org/abs/1305.6334