  Magnetic skyrmions are topological magnetic structures, which exhibit
quasi-particle properties and can show enhanced stability against perturbation
from thermal noise. Recently, thermal Brownian diffusion of these
quasi-particles has been found in continuous films and applications in
unconventional computing have received significant attention, which however
require structured elements. Thus, as the next necessary step, we here study
skyrmion diffusion in confined geometries and find it to be qualitatively
different: The diffusion is governed by the interplay between the total number
of skyrmions and the structure geometry. In particular, we ascertain the effect
of circular and triangular geometrical confinement and find that for triangular
geometries the behavior is drastically different for the cases when the number
of skyrmions in the element is either commensurate or incommensurate with a
symmetric filling of the element. This influence of commensurability is
corroborated by simulations of a quasi-particle model.
