Spin dynamics dominated by resonant tunneling into molecular states

Optical lattices and Feshbach resonances are two of the most ubiquitously-used tools in atomic physics, allowing for the precise control, discrete confinement, and broad tunability of interacting atomic systems. Using a quantum simulator of lithium-7 atoms in an optical lattice, we investigate Heisenberg spin dynamics near a Feshbach resonance. We find novel resonance features in spin-spin interactions that can only be explained by lattice-induced resonances, which have never been observed before. We use these resonances to adiabatically convert atoms into molecules in excited bands. Further, we also report the first experimental evidence for off-site contact interactions in an optical lattice. Lattice-induced resonances should be of general importance for studying strongly-interacting quantum many-body systems in optical lattices.