Devil's staircase of facets on the surface of 4He crystals

According to Landau, at T=0 the equilibrium crystal surface consists of an infinite number of facets lying in all directions with rational Miller indices-the so-called devil's staircase phenomenon. We have discovered 11 new types of facets on the surface of 4He crystals, in addition to the three observed before. Some of the new facets are of very high order, lying at angles as small as 4 degrees to the basal c facet, thus forming the predicted devil's staircase. The estimated step energies depend rather weakly on interplanar distance which we explain by the strong anisotropy of the steps.