Control of molecular excitations in nanotube-heterostructure transistors

Current-induced molecular excitations play an important role in molecular-electronics devices like the resonant-tunneling nanotube-heterostructure transistor [Solid State Comm. 116 (2000) 569, Science 293 (2001) 76.]. The nonlinear transport through a resonant level stimulates local molecular vibrations because the single-electron injection modifies the chemical bonding. I report and interpret out-of-equilibrium Green-function calculations to predict the resulting current-induced molecular stimulation as a function of the excitation frequency, the applied bias, and the electrostatic-gate potential. I show that the out-of-equilibrium operating conditions voids the traditional (detailed balance) transition rules (relating spontaneous and stimulated emission/absorption). Finally, I show that the out-of-equilibrium results for the current stimulation permit a frequency-selective excitation of the nanotube vibrations.