The effect of inter-valley scattering on weak localisation in graphene

We experimentally demonstrate that weak localisation (WL) exists in graphene fabricated by mechanical exfoliation at different carrier densities. We show that it is controlled not only by inelastic dephasing mechanisms, but also by elastic intra- and inter-valley scattering. By reducing the width of the graphene sample, inter-valley scattering is found to be limited by the sample boundaries. Intravalley scattering, which suppresses WL in one valley, is found to be much faster than inter-valley scattering. In the Dirac point, where there is a zero-net carrier density, we observe a distinct change in both elastic and inelastic scattering.