Scattering by flexural phonons in suspended graphene under back gate induced strain

TL;DR

This paper investigates how flexural phonons affect electron scattering in suspended graphene, showing that strain alters phonon dispersion and significantly impacts charge transport, with implications for mobility in strained samples.

Contribution

The study provides a theoretical analysis of strain effects on flexural phonon dispersion and electron scattering in suspended graphene, linking these effects to experimental observations.

Findings

Flexural phonons cause significant electron scattering in unstrained graphene.

Strain changes phonon dispersion from quadratic to linear, reducing scattering.

Back gate induced strain can improve electron mobility by modifying phonon behavior.

Abstract

We have studied electron scattering by out-of-plane (flexural) phonon modes in doped suspended graphene and its effect on charge transport. In the free-standing case (absence of strain) the flexural branch shows a quadratic dispersion relation, which becomes linear at long wavelength when the sample is under tension due to the rotation symmetry breaking. In the non-strained case, scattering by flexural phonons is the main limitation to electron mobility. This picture changes drastically when strains above $\bar{u}=10^{-4} n(10^{12}\,\text{cm}^{-2})$ are considered. Here we study in particular the case of back gate induced strain, and apply our theoretical findings to recent experiments in suspended graphene.