arXiv:cond-mat/0509093 · Physical Review A
Two-body problem in periodic potentials
Michiel Wouters, Giuliano Orso
Abstract
We investigate the problem of two atoms interacting via a short range $s$-wave potential in the presence of a deep optical lattice of arbitrary dimension $D$. Using a tight-binding approach, we derive analytical results for the properties of the bound state and the scattering amplitude. We show that the tunneling through the barriers induces a dimensional crossover from a confined regime at high energy to an anisotropic three-dimensional regime at low energy. The critical value of the scattering length needed to form a two-body bound state shows a logaritmic dependence on the tunneling rate for $D=1$ and a power law for $D>1$. For the special case $D=1$, we also compare our analytical predictions with exact numerics, finding remarkably good agreement.