Atomic seesaws.

The dynamics of two types of atomic seesaws are studied by open feedback loop scanning tunneling microscopy. The first type of atomic seesaw is a regular Ge dimer of the dimer reconstructed Ge(001) surface and the second type of atomic seesaw is a dimer located on the ridges of Au induced nanowires on a Ge(001) surface. On the bare Ge(001) surface the flip-flop motion of the dimers is induced by phasons, which perform a one-dimensional random walk along the substrate dimer rows. The phasons on the Au induced nanowires ridges are pinned and therefore only a limited number of dimers exhibit flip-flop behavior for the Au/Ge(001) system.