  Diffusion across surfaces generally involves motion on a vibrating but
otherwise stationary substrate. Here, using molecular dynamics, we show that a
layered material such as graphene opens up a new mechanism for surface
diffusion whereby adsorbates are carried by propagating ripples via a motion
similar to surfing. For water nanodroplets, we demonstrate that the mechanism
leads to exceedingly fast diffusion that is 2-3 orders of magnitude faster than
the self-diffusion of water molecules in liquid water. We also reveal the
underlying principles that regulate this new mechanism for diffusion and show
how it also applies to adsorbates other than water, thus opening up the
prospect of achieving fast and controllable motion of adsorbates across
material surfaces more generally.
