Appearance of Large Amplitude Current Dynamics as a Result of Bragg   Reflection in Carbon Nanotubes
  We report on theoretical analysis of large amplitude current dynamics due to Bragg reflections in carbon nanotubes exposed to an external electric field. Using the kinetic equation with constant relaxation time, an analytical expression for the current density is obtained. Our results suggest that Bloch gain exists up to frequencies on the order of the Bloch frequency. We noted that due to the high density of states of conduction electrons in metallic carbon nanotubes and the specific dispersion law inherent in hexagonal crystalline structure result in a uniquely high frequency gain than the corresponding values for semiconducting ones. We suggest that this phenomenon can be used for domainless multiplication of the frequency of an electromagnetic signal at room temperature 
S. S. Abukari, S. Y. Mensah, N. G. Mensah, K. W. Adu, M. Rabiu, K. A.   Dompreh and A. Twum
cond-mat.mes-hall