When describing the dynamics of particles in optical lattices, the recoil energy arises as the natural energy scale. It would be interesting to realize in experiments optical lattices with sub-wavelength spacing, in order to raise the energy scale of naturally weak processes such as super-exchange.

I will present a scheme to realize lattice potentials of sub-wavelength spacing for ultracold atoms of the Lanthanide family. It is based on spin-dependent optical lattices with a time-periodic modulation. The atomic motion can be described by the combined action of an effective, time-independent, lattice of small spacing, together with a micro-motion associated with the time-modulation. A numerical simulation shows that an atomic gas can be adiabatically loaded into the effective lattice ground state, for timescales comparable to the ones required for adiabatic loading of standard optical lattices. We generalize our scheme to a two-dimensional geometry, leading to Bloch bands with non-zero Chern numbers.