Effects of Different Junction Parameters on Junction Conductances of Crossed Metallic Carbon Nanotubes

Abstract

We have studied the effect of different junction parameters on the junction conductancesmade of two crossed metallic carbon nanotubes. We have found that because of the intrinsicasymmetries of the junction, forward and backward tunneling between one tube and the otherare unequal. Passing a current in one tube leaded to the development of non zero voltageacross the other one, a zero field Hall like conductance for the junction was found. We havefound that this zero field Hall conductance relates to the contact conductance of the junction.The result also shows that the electronic properties of the junction sensitively depend on thedegree of matching between the tube lattices. This matching is controlled by the crossingangel, which resulted in an intertube conductance that varied by an order of magnitude fordifferent angles. We have derived a tunneling matrix element that coupled the low energyelectronic states on the two tubes. The magnitude of the coupling was determined by theintertube separation of the crossing angle. We have found that the intrinsic symmetries of thejunction created a discrepancy between the forward and backward hopping between thetubes. Using Landauer-Buttiker formalism, we have calculated the different conductances ofthe four terminal junctions. We have found that the contact conductance scaled inversely withthe zero field Hall conductance of the junction. We have also found that the two crucialparameters in determining the conductance are the tube chiralities and the crossing angle. Theobtained results were found in good agreement with previously obtained results