Local vibrational excitation through extended electronic states at a germanium surface.

Atomic motion through excitation of extended surface electronic states on Ge(001) is studied using extraction of electrons by scanning tunneling microscopy and density functional theory. Single-electron excitation into the surface states nonlocally alters the tilting orientation of the surface Ge dimer, and the change rate depends on the excitation energy. Theoretical investigations identify the excited electronic states for the dimer motion, and clarify the strong coupling between the surface state electrons and a local vibrational mode of the dimer for changing the tilting orientation.