Temperature Effects on Dynamical Conductivity of Graphene Based Systems

Abstract

We have investigated dynamical conductivity of graphene based systems; Single Layer Graphene (SLG), Bilayer Graphene (BLG) and Single Layer Gapped Graphene (SLGG), at zero and finite temperatures by taking into the account screening effects within the Random Phase Approximation (RPA). Rσq,ω and Rσq,ω show peaks that correspond to single particle excitations (SPE) and collective excitations (CE) respectively. In SLG, SPE positions are observed at ωħ≈0.5εf,εf∧1.5εf for q0.5kf,kf∧1.5kf respectively for all values of temperature. The peak height increases with increasing electron momentum and temperature. We noticed that for finite momentumq0.5kf∧kf, the peak height is maximum for T=0K and minimum for T=0.5Tf while that for T=Tf is intermediate. We also noticed that Rσq,ω peaks are blue shifted at high temperature for all graphene systems. In case of BLG, Landau undamped peak has been observed at T=0 for finite momentumq=0.3kf which becomes smooth at T=0.5Tf∧Tf. For q=0.8kf, Landau damped plasmon peaks have also been observed for all values of temperature. No major changes are observed in case of SLGG, with respect to SPE and CE peaks positions and heights specifically due to small change in band gap value incorporated here.