Doublons Instability in the Presence of Impurities

In the presence of strong interactions, particles can bind in pairs forming what became known as doublons. A doublon moves together as a single particle, but contrary to it, doublons move slowly. They emerge in common models of condensed matter physics, such as the anisotropic Heisenberg model and the Bose-Hubbard model. We show that doublons are very stable and do not split up even when this would not violate energy conservation. We illustrate our results using one- and two-dimensional spin models in the presence of impurities.