Slow noncollinear Coulomb scattering in the vicinity of the Dirac point in graphene

TL;DR

This study investigates Coulomb scattering near the Dirac point in graphene, revealing that noncollinear scattering is significantly slower than collinear scattering, especially at low energies, which could benefit infrared and THz device applications.

Contribution

It provides new insights into the slow noncollinear Coulomb scattering dynamics in near-intrinsic graphene near the Dirac point.

Findings

Collinear Coulomb scattering rapidly thermalizes carriers.

Noncollinear scattering near the Dirac point is much slower, on a picosecond timescale.

Carrier-optical-phonon processes are suppressed at low photon energies.

Abstract

The Coulomb scattering dynamics in graphene in energetic proximity to the Dirac point is investigated by polarization resolved pump-probe spectroscopy and microscopic theory. Collinear Coulomb scattering rapidly thermalizes the carrier distribution in k-directions pointing radially away from the Dirac point. Our study reveals, however, that in almost intrinsic graphene full thermalization in all directions relying on noncollinear scattering is much slower. For low photon energies, carrier-optical-phonon processes are strongly suppressed and Coulomb mediated noncollinear scattering is remarkably slow, namely on a ps timescale. This effect is very promising for infrared and THz devices based on hot carrier effects.