Dependence of quantum-Hall conductance on the edge-state equilibration position in a bipolar graphene sheet

By using four-terminal configurations, we investigated the dependence of longitudinal and diagonal resistances of a graphene p-n interface on the quantum-Hall edge-state equilibration position. The resistance of a p-n device in our four-terminal scheme is asymmetric with respect to the zero point where the filling factor (nu) of the entire graphene vanishes. This resistance asymmetry is caused by the chiral direction dependent change in the equilibration position and leads to a deeper insight into the equilibration process of the quantum-Hall edge-states in a bipolar graphene system.