Effects of optical and surface polar phonons on the optical conductivity of doped graphene

TL;DR

This study investigates how optical and surface polar phonons influence the optical conductivity of doped graphene, revealing significant phonon-assisted absorption and temperature-dependent effects that vary with substrate and doping levels.

Contribution

It provides a detailed analysis of phonon effects on graphene's optical properties using the Kubo formalism, highlighting the importance of electron-phonon interactions in doped graphene.

Findings

Midgap absorption can reach 20-25% of universal conductivity at room temperature.

Midgap absorption depends strongly on substrate and doping levels.

Temperature increases midgap absorption and broadens the Drude peak, reducing Drude weight.

Abstract

Using the Kubo linear response formalism, we study the effects of intrinsic graphene optical and surface polar phonons (SPPs) on the optical conductivity of doped graphene. We find that inelastic electron-phonon scattering contributes significantly to the phonon-assisted absorption in the optical gap. At room temperature, this midgap absorption can be as large as 20-25% of the universal ac conductivity for graphene on polar substrates due to strong electron-SPP coupling. The midgap absorption, moreover, strongly depends on the substrates and doping levels used. With increasing temperature, the midgap absorption increases, while the Drude peak, on the other hand, becomes broader as inelastic electron-phonon scattering becomes more probable. Consequently, the Drude weight decreases with increasing temperature.