Skyrmion molecular crystals and superlattices on triangular substrates

Using atomistic simulations, we show that different types of skyrmion states called skyrmion molecular crystals and skyrmion superlattices can be realized on triangular substrates when there are two or three skyrmions per substrate minimum. We find that as a function of the magnetic field and substrate periodicity, a remarkably wide variety of ordered phases appear similar to those found in colloidal or Wigner molecular crystals, including ferromagnetic and herringbone states. The ability of the skyrmions to annihilate, deform, and change size gives rise to a variety of superlattice states in which a mixture of different skyrmion sizes and shapes produces bipartite or more complex lattice structures. Our results are relevant for skyrmions on structured triangular substrates or in magnetic arrays, or for skyrmions in moiré materials.