Symmetry effects on the conductance of nanotube junctions

The ballistic conductance of various two-terminal and three-terminal carbon nanotube systems is calculated within the Landauer formalism. Using only m etallic nanotubes as terminals, it is shown that only a subset of juctions topologies preserve the metallic function. This behavior is rationalized bo th in the two-terminal and three-terminal systems through symmetry consider ations.