The role of interaction-induced tunneling in the dynamics of polar lattice bosons

Inter-site dipolar interactions induce, even in absence of disorder, an intriguing non-ergodic dynamics for dipolar bosons in an optical lattice. We show that the inherent dipole-induced density-dependent tunneling, typically neglected, plays a crucial role in this dynamics. For shallow-enough lattices, the delocalization stemming from the interaction-induced hopping overcomes the localization induced by inter-site interactions. As a result, in stark contrast to the more studied case of hard-core bosons, delocalization is counter-intuitively strengthen when the dipolar strength increases. Furthermore, the quasi-cancellation between bare and interaction-induced tunneling may lead, near a lattice-depth-dependent value of the dipole strength, to an exact decoupling of the Hilbert space between ergodic hard-core states and strongly non-ergodic soft-core ones. Our results show that interaction-induced hopping should play a crucial role in future experiments on the dynamics of polar lattice gases.