Control of bound-pair transport by periodic driving

Abstract

We investigate the effect of periodic driving by an external field on systems with attractive pairing interactions. These include spin systems (such as the ferromagnetic $XXZ$ model) as well as ultracold fermionic atoms described by the attractive Hubbard model. We show that a well-known phenomenon seen in periodically driven systems---the renormalization of the exchange coupling strength---acts selectively on bound pairs of spins (atoms), relative to magnon (bare atom) states. Thus one can control the direction and speed of transport of bound pair relative to magnon (unpaired) atom states, and thus coherently achieve spatial separation of these components. Applications to recent experiments on transport with fermionic atoms in optical lattices which consist of mixtures of bound pairs and bare atoms are discussed.