  We study the low-energy electronic properties of a junction made of two
crossed metallic carbon nanotubes of general chiralities. We derive a tight
binding tunneling matrix element that couples low-energy states on the two
tubes, which allows us to calculate the contact conductance of the junction. We
find that the intrinsic asymmetries of the junction cause the forward and
backward hopping probabilities from one tube to another to be different. This
defines a zero-field Hall conductance for the junction, which we find to scale
inversely with the junction contact conductance. Through a systematic study of
the dependence of the junction conductance on different junction parameters, we
find that the crossing angle is the dominant factor which determines the
magnitude of the conductance.
