Creating State-Dependent Lattices for Ultracold Fermions by Magnetic Gradient Modulation

We demonstrate a versatile method for creating state-dependent optical lattices by applying a magnetic field gradient modulated in time. This allows for tuning the relative amplitude and sign of the tunneling for different internal states. We observe substantially different momentum distributions depending on the spin state of fermionic 40K atoms. Using dipole oscillations, we probe the spin-dependent band structure and find good agreement with theory. In situ expansion dynamics demonstrate that one state can be completely localized while others remain itinerant. A systematic study shows negligible heating and lifetimes of several seconds in the Hubbard regime.