Energy relaxation of hot Dirac fermions in graphene

Abstract

We develop a theory for the energy relaxation of hot Dirac fermions in graphene. We obtain a generic expression for the energy relaxation rate due to electron-phonon interaction and calculate the power loss due to both optical and acoustic phonon emission as a function of electron temperature ${T}_{\text{e}}$ and density $n$. We find an intrinsic power loss weakly dependent on carrier density and nonvanishing at the Dirac point $n=0$, originating from interband electron-optical phonon scattering by the intrinsic electrons in the graphene valence band. We obtain the total power loss per carrier $\ensuremath{\sim}{10}^{\ensuremath{-}12}--{10}^{\ensuremath{-}7}\text{ }\text{W}$ within the range of electron temperatures $\ensuremath{\sim}20--1000\text{ }\text{K}$. We find optical (acoustic) phonon emission to dominate the energy loss for ${T}_{\text{e}}>(<)200--300\text{ }\text{K}$ in the density range $n={10}^{11}--{10}^{13}\text{ }{\text{cm}}^{\ensuremath{-}2}$.