We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by Büchler et al. [Nature Phys. 3, 726 (2007)]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely by long-ranged three-body terms. The resulting phase diagram shows a sequence of solid and supersolid phases. Our findings are directly relevant for future experimental implementations and open a new route towards the discovery of a lattice supersolid phase in experiment.
We show that microwave shielding, which enables collisionally stable ultracold polar molecules, also leads to genuine nonadditive three-body interactions comparable to the shielding interaction itself. Their magnitude, sign, and geometrical dependence can be flexibly controlled through microwave parameters and orientation. Interaction strengths can reach the ten kilohertz-scale for ultrapolar molecules in typical optical lattices. The nonadditive three-body interactions can stabilize novel many-body phases, and should be accounted for in quantum simulation with microwave shielded molecules.
Few-body bound states have been extensively explored in cold atomic gases with a desire to realize large molecular complexes. Here, we investigate the formation of trimers in an infinite one-dimensional lattice with hard-core two- and three-body interactions of relevance to Rydberg atoms and polar molecules in optical lattices, and other physical systems such as the fractional Hall states. We determine the stability regions for attractively and repulsively bound trimers. We discover a regime of large spatially extended trimers that are stabilized by the interplay of attractive two-body,
U , and repulsive three-body,
V , interactions and persist despite extremely large
V. These bound states present a new direction in the search for large few-body complexes in cold atoms.