Long range substrate mediated mass transport on metal surfaces induced by adatom clusters

Mass transport at surfaces can proceed either (i) by hopping diffusion of atoms on top of the surface from one site to another or (ii) by propagation of small displacements from one atom to the next within the topmost atomic layer. In the latter case, a long range substrate mediated mass transport has been postulated but never observed explicitly. Experimental and theoretical evidence is shown here for the occurrence of such a mechanism on the reconstructed Au(111) surface, where the movement is shown to be well described by a soliton.