Abstract Submitted to the NANOTUBE-99 Workshop:

The contact between carbon nanotubes and metal can occur at the end of the tube (end-contact) or along the circumference of the tube (side-contact). The end-contacts usually involve strong interaction between the metal and carbon atoms at the end of the nanotube. On the other hand, the side-contacts involve weak coupling either between a tube lying on a metal contact or dipped in a liquid metal. In this talk, we discuss the modeling of transport through side-contacted junctions. If the metal-nanotube interface is sufficiently ordered, we find that k-vector conservation plays an important role in determining the coupling, with the physics depending on the area of contact, tube diameter and chirality. We show that:
(a) The difference between small and large diameter nanotubes making uniform contact around the circumference to the metal is that while in the former wave vector conservation is important only in the axial direction, in the latter it is important along both the axial and circumferential directions.
(b) Armchair and zigzag tubes have a cut-off value of the metal Fermi wave vector (below which conductance is small) equal to $2\pi/3a_0$ and zero, respectively. For chiral tubes, the cut-off value of the metal Fermi wave vector lies in between these two limits, with the value decreasing with increase in chiral angle.
(c) Experiments have shown increase in conductance with increase in contact length. We demonstrate two scenarios that can lead to this observation, one with and the other without disorder.

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