  Molecular organic materials offer the promise of novel electronic devices but
also present challenges for understanding charge transport in narrow band
systems. Low temperature studies elucidate fundamental transport processes. We
report the lowest temperature field effect transport results on a crystalline
oligomeric organic material, rubrene. We find field effect switching with
on-off ratio up to 10^7 at temperatures down to 10 K. Gated transport shows a
factor of ~10 suppression of the thermal activation energy in 10-50 K range and
nearly temperature independent resistivity below 10 K.
