Temperature dependence of electron density and electron-electron interactions in monolayer epitaxial graphene grown on SiC.

We report carrier density measurements and electron-electron ( e - e ) interactions in monolayer epitaxial graphene grown on SiC. The temperature ( T )-independent carrier density determined from the Shubnikov-de Haas (SdH) oscillations clearly demonstrates that the observed logarithmic temperature dependence of Hall slope in our system must be due to e - e interactions. Since the electron density determined from conventional SdH measurements does not depend on e - e interactions based on Kohn's theorem, SdH experiments appear to be more reliable compared with the classical Hall effect when one studies the T dependence of the carrier density in the low T regime. On the other hand, the logarithmic T dependence of the Hall slope δ R xy /δ B can be used to probe e - e interactions even when the conventional conductivity method is not applicable due to strong electron-phonon scattering.