Vibration of dimer on Ge(001) surface excited coherently by tunneling current of scanning tunneling microscopy

The vibration of a dimer on a Ge(001) surface with a high vibrational number excited coherently by tunneling current of scanning tunneling microscopes (STMs), is theoretically investigated. The transformation of the local structures reported in STM experiments is shown to be driven by the dimer vibration excited coherently by the tunneling current of STM. The sample bias voltage of STM above which the transformation to the p(2×2) structure is able to be observed in the experiments, is semiquantitatively reproduced by the quasi-one-dimensional character of the π*-band. We show that the excitation rate has a term that does not decay with the distance from the STM tip for the one-dimensional band. The contrasting difference in shape of the transformed region that depends on the sign of the bias voltage observed in the experiments is explained by the dimensionalities of the π*-band and the π-band on the Ge(001) surface.