Dissipative Binding of Lattice Bosons through Distance-Selective Pair Loss

We show that in a gas of ultracold atoms distance selective two-body loss can be engineered via the resonant laser excitation of atom pairs to interacting electronic states. In an optical lattice this leads to a dissipative master equation dynamics with Lindblad jump operators that annihilate atom pairs with a specific interparticle distance. In conjunction with coherent hopping between lattice sites this unusual dissipation mechanism leads to the formation of coherent long-lived complexes that can even exhibit an internal level structure which is strongly coupled to their external motion. We analyze this counterintuitive phenomenon in detail in a system of hard-core bosons. While current research has established that dissipation in general can lead to the emergence of coherent features in many-body systems our work shows that strong nonlocal dissipation can effectuate a binding mechanism for particles.

Figure 1

(a) Level scheme of a pair of atoms laser-excited to Rydberg states. The pair state $|ee⟩$ is excited via an effective two-photon resonance from the state $|gg⟩$ when the distance between the two atoms is equal to the critical distance $r_c$. Mechanical forces due to the strongly repulsive Rydberg-Rydberg interaction and radiative decay (at total rate $2{\Gamma }_{\mathrm{Ryd}}$ for two excited atoms) lead to loss of the atom pair. (b) In an optical lattice this leads to a distance selective loss of atoms. Shown is a pair of atoms that is created at the critical distance after a hopping event, leading to a two-body loss.

Figure 2

Numerical propagation of two hard core bosons under the original master equation [with the dissipator (1)]. The graphs show the time evolution of the mean number of atoms on each lattice site. The initial state is ${\sigma }_1^{+}{\sigma }_2^{+}|\mathrm{vac}⟩$, the critical radius is ${\lambda }_c=3$ and the lattice has 20 sites and open boundaries. Weak dissipation leads to quick loss of the particles from the lattice. Strong dissipation results in an overall reduction of the decay and imposes a constraint on the coherent evolution that effectuates a binding mechanism.