Nonlinear Interlayer Transport in the Aligned Carbon Nanotube Films and Graphite

Interlayer tunneling spectroscopy on graphite stacked junctions and on aligned carbon nanotube (ACN) films shows universal zero bias anomaly (dip) for both type of objects. For graphite this anomaly disappears above 30K, while for aligned nanotube films it persists up to 350K. We consider this anomaly as a pseudogap that appears due to the presence of interlayer correlated state.