  The electrical conductivity of a macroscopic assembly of nanomaterials is
determined through a complex interplay of electronic transport within and
between constituent nano-objects. Phonons play dual roles in this situation:
their increased populations tend to reduce the conductivity via electron
scattering while they can boost the conductivity by assisting electrons to
propagate through the potential-energy landscape. Here, we identify a
phonon-assisted coherent electron transport process between neighboring
nanotubes in temperature-dependent conductivity measurements on a macroscopic
film of armchair single-wall carbon nanotubes. Through atomistic modeling of
electronic states and calculations of both electronic and phonon-assisted
junction conductances, we conclude that phonon-assisted conductance is the
dominant mechanism for the observed high-temperature transport. The unambiguous
manifestation of coherent intertube dynamics proves a single-chirality armchair
nanotube film to be a unique macroscopic solid-state ensemble of nano-objects
promising for the development of room-temperature coherent electronic devices.
