Bath-induced band decay of a Hubbard lattice gas

Dissipation is introduced to a strongly interacting ultracold bosonic gas in the Mott-insulator regime of a three-dimensional spin-dependent optical lattice. A weakly interacting superfluid comprised of atoms in a state that does not experience the lattice potential acts as a dissipative bath coupled to the lattice atoms via collisions. Lattice atoms are excited to a higher-energy band via Bragg transitions, and the resulting bath-induced decay is measured using the atomic quasimomentum distribution. A competing but slower intrinsic decay mechanism arising from collisions between lattice atoms is also investigated. The measured bath-induced decay rate is compared with the predictions of a weakly interacting model with no free parameters. The presence of intrinsic decay, which cannot be accommodated within this framework, signals that strong interactions may play a central role in the lattice-atom dynamics.