Transport and Coulomb drag for two interacting carbon nanotubes

We study nonlinear transport for two coupled one-dimensional quantum wires or carbon nanotubes described by Luttinger liquid theory. Transport properties are shown to crucially depend on the contact length $L_c$. For a special interaction strength, the problem can be solved analytically for arbitrary $L_c$. For point-like contacts and strong interactions, a qualitatively different picture compared to a Fermi liquid emerges, characterized by zero-bias anomalies and strong dependence on the applied cross voltage. In addition, pronounced Coulomb drag phenomena are important for extended contacts.