Magnetomotive instability and generation of mechanical vibrations in suspended semiconducting carbon nanotubes

We investigate the electromechanics of a freely suspended semiconducting carbon nanotube subjected to a magnetic field H in the currentbiased regime and show that self-excitation of mechanical nanotube vibrations can occur if H exceeds a critical value H_c of the order of 10-100mT. The effect can be detected by measuring the magnetic field dependence of the timeaveraged voltage drop across the nanotube, which has a singularity at H = H_c. We discuss the applications of the device as an active, tuneable radiofrequency oscillator. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.