Probing two-body interactions in a deep three-dimensional optical lattice

Experimental control and readout of two-body interacting systems can enhance understanding of many-body states. Here, we use a deep 3D optical lattice to form isolated pairs of fermionic 40K atoms. We report on two experiments that probe s- and p-wave interacting pair states in this two-body system.

First, we present measurements of elastic p-wave interactions of spin-polarized fermions near a p-wave Feshbach resonance. The suppression of three-body loss through lattice confinement enables observation of unitary p-wave interactions as well as Rabi oscillations between the free-atom and Feshbach molecule states. Results agree well with solutions using a p-wave pseudopotential. These measurements provide a starting point for realizing novel p-wave interacting many-body states in an optical lattice.

Second, we describe measurements of s-wave spatial correlations of atoms in fermionic pair states through photoexcitation of isolated Feshbach molecules. We tune interactions via an s-wave Feshbach resonance, and observe that the rate of photoexcitation varies strongly with the interaction strength. The resonant photoexcitation rate is expected to depend on the s-wave contact, which can be compared to measurements of on-site interaction energy through universal contact relations. This experimental technique could be used as a precise probe of molecular structure at high magnetic fields or applied to measure correlations in many-body lattice states.