Temperature Dependence of Electron Density and Electron-Electron Interactions in Monolayer Epitaxial Graphene on SiC
Chieh-Wen Liu1,2*, Chiashain Chuang1, Yanfei Yang1, Randolph E. Elmquist1, Yi-Ju Ho2, Hsin-Yen Lee3, Chi-Te Liang2,3
1National Institute of Standards and Technology (NIST), Gaithersburg, MD, USA
2Graduate Institute of Applied Physics, National Taiwan University, Taipei, Taiwan
3Department of Physics, National Taiwan University, Taipei, Taiwan
* presenting author:Chieh-Wen Liu, email:liuchiehwen@gmail.com
We report electron-electron (e-e) interactions and carrier density measurements in monolayer epitaxial graphene grown on SiC. Shubnikov-de Hass (SdH) oscillations yield a temperature (T)-independent carrier density, which clearly demonstrates that the observed logarithmic temperature dependence of the 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, SdH experiments appear to be more reliable than classical Hall effect measurements when one studies the T dependence of the carrier density in the low T region. On the other hand, the logarithmic T dependence of the Hall slope δRxy/δB can be used to probe e-e interactions even when the conventional conductivity method is not applicable due to strong electron-phonon scattering. Our work should shed light on possible low-T charge trapping which could be detrimental to various quantum measurements and most importantly to graphene-based device stability.

Keywords: Graphene, Electron-electron interactions, Carrier density