van Hove singularities in disordered multichannel quantum wires and nanotubes

We present a theory for the van Hove singularity (VHS) in the tunneling density of states (TDOS) of disordered multichannel quantum wires, in particular multiwall carbon nanotubes. We assume close-by gates that screen off electron-electron interactions. Diagrammatic perturbation theory within the noncrossing approximation yields analytical expressions governing the disorder-induced broadening and shift of VHS’s as new subbands are opened. This problem is nontrivial because the (lowest-order) Born approximation breaks down close to the VHS. Interestingly, compared to the bulk case, the boundary TDOS shows drastically altered VHS’s, even in the clean limit.