Magnetoresistance in single-layer graphene: weak localization and universal conductance fluctuation studies

We report measurements of magnetoresistance in single-layer graphene as a function of gate voltage (carrier density) at 250 mK. By examining signatures of weak localization (WL) and universal conductance fluctuations (UCF), we find a consistent picture of phase coherence loss due to electron-electron interactions. The gate dependence of the elastic scattering terms suggests that the effect of trigonal warping, i.e. the nonlinearity of the dispersion curves, may be strong at high carrier densities, while intra-valley scattering may dominate close to the Dirac point. In addition, a decrease in UCF amplitude with decreasing carrier density can be explained by a corresponding loss of phase coherence.