Abstract
We investigate optical transitions of noninteracting electron systems consisting of two symmetric energy bands touching each other at the Fermi energy (e.g., graphene at half-filling). Optical conductivity is obtained using Kubo formula at zero temperature. We show that for particles whose pseudospin direction is determined solely by the direction of their momentum, the optical conductivity has power-law frequency dependence with the exponent where is the dimension of the system and is the dynamical exponent. According to our result two-dimensional systems with the above pseudospin characteristics always exhibit frequency-independent optical conductivity.
- Received 8 February 2013
DOI:https://doi.org/10.1103/PhysRevB.87.125425
©2013 American Physical Society