Transport properties of monolayer and bilayer graphene p–n junctions with charge puddlesin the quantum Hall regime

Abstract

Recent experiments have confirmed that the electron–hole inhomogeneity in graphene is anew type of charge disorder. Motivated by such confirmation, we theoretically study thetransport properties of a monolayer graphene (MLG) based p–n junction and a bilayergraphene (BLG) p–n junction in the quantum Hall regime where electron–holepuddles are considered. By using the non-equilibrium Green function method,both the current and conductance are obtained. We find that, in the presence ofthe electron–hole inhomogeneity, the lowest quantized conductance plateau ate2/h emerges in the MLG p–n junction under very small charge puddle disorder strength. Fora BLG p–n junction, however, the conductance in the p–n region is enhancedwith charge puddles, and the lowest quantized conductance plateau emerges at2e2/h. Besides, when an ideal quantized conductance plateau is formed for aMLG p–n junction, the universal conductance fluctuation is found to be2e2/3h. Furthermore, we also investigate the influence of Anderson disorder on such p–n junctionsand the comparison and discussion are given accordingly. To compare the two models withdifferent types of disorder, we investigate the conductance distribution specially. Finally theinfluence of disorder strength on the conductance of a MLG p–n junction is investigated.