Electronic structure of carbon nanotube ropes

We present a tight-binding theory to analyze the motion of electrons betwee n carbon nanotubes bundled into a carbon nanotube rope. The theory is devel oped starting from a description of propagating Bloch waves on ideal tubes, and the effects of intertube motion are treated perturbatively on this bas is. Expressions for the interwall tunneling amplitudes between states on ne ighboring tubes are derived which show the dependence on chiral angles and intratube crystal momenta. We find that conservation of crystal momentum al ong the tube direction suppresses interwall coherence in a carbon nanorope containing tubes with random chiralities, Numerical calculations are presen ted which indicate that electronic states in a rope are localized in the tr ansverse direction, with a coherence length corresponding to a tube diamete r.