Conductivity of interacting massless Dirac particles in graphene: Collisionless regime

Understand

We provide detailed calculation of the a.c.

• conductivity in the case of 1/r-Coulomb interacting massless Dirac particles in graphene in the collisionless limit when \omega >> T.
• The analysis of the electron self-energy, current vertex function and polarization function, which enter into the calculation of physical quantities including the a.c.
• conductivity, is carried out by checking the Ward-Takahashi identities associated with the electrical charge conservation and making sure that they are satisfied at each step.