Spontaneous oscillation of current in fullerene molecular junctions

We study the correlated phenomena of resonant conduction and current-driven dynamics in Au C60 Au molecular junctions from first principles. A significant resonant component of the transmission gives rise to vibrations of the C60 center of mass between the electrodes. Along with strong dependence of the transmission on the location of the fullerene within the junction, the current-driven vibration leads to oscillating current in the THz regime. An interesting interplay between conductance channels of different symmetries and different degrees of spatial localization results in marked dependence of the transmission characteristics on the orientation of the C60 with respect to the gold surface. Whereas the equilibrium orientation gives rise to Breit Wigner line shapes and well-characterized conductance channels, the loss of reflection symmetry at other orientations results in more complex electronic dynamics. The physical origin and the practical consequences of these findings are discussed.