Slow Noncollinear Coulomb Scattering in the Vicinity of the Dirac Point in Graphene

Phys Rev Lett. 2016 Aug 19;117(8):087401. doi: 10.1103/PhysRevLett.117.087401. Epub 2016 Aug 15.

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 time scale. This effect is very promising for infrared and THz devices based on hot carrier effects.