Unconventional optical response in monolayer graphene due to dominant intraband scattering

Scattering dynamics influences the graphene's transport properties and inhibits the charge carrier deterministic behavior. The intra/interband scattering mechanisms are vital for graphene's optical conductivity response under specific considerations of doping. In this study, we systematically explored the impact of scattering on optical conductivity using a semiclassical multiband Boltzmann equation, incorporating both electron-electron and electron-phonon interactions collectively with a single phenomenological relaxation time constant. We found unconventional characteristics of linear optical response with a significant deviation from the universal conductivity (e2/4ℏ) in doped monolayer graphene. This is explained through phenomenological relaxation rates under low doping regime with dominant intraband scattering. Such novel optical responses vanish at high temperatures or overdoping conditions due to strong Drude behavior. With the aid of approximations around Dirac points we have developed analytical formalism for many-body interactions and are in good agreement with the Kubo approaches.