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 that persists up to 350K. We consider this anomaly as a pseudogap that appears due to a presence of interlayer correlated state. In a presence of magnetic field of 1-10T oriented across the layers we found characteristic peaks on interlayer tunneling spectra of graphite mesas. Their voltage position and square root dependence on magnetic field let us to identify the origin of those peaks to be related with interlayer tunneling between Landau levels (LLs) in graphite typical for Dirac fermions in graphene.