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.