Abstract
We explore the feasibility of optically forming long-range tetratomic and larger polyatomic molecules in their ground electronic state from ultracold pairs of polar molecules aligned by external fields. Depending on the relative orientation of the interacting diatomic molecules, we find that a tetratomic can be formed either as a weakly bound complex in a very extended halo state or as a pure long-range molecule composed of collinear or nearly-collinear diatomic molecules. The latter is a novel type of tetratomic molecule comprised of two diatomic molecules bound at long intermolecular range and predicted to be stable in cold and ultracold regimes. Our numerical studies were conducted for ultracold KRb and RbCs, resulting in production of (KRb)$_2$ and (RbCs)$_2$ complexes, respectively. Based on universal properties of long-range interactions between polar molecules, we identify triatomic and tetratomic linear polar molecules with favorable ratio of dipole and quadrupole moments for which the apporach could be generalized to form polyatomic molecules.
Highlights
Ultracold polar molecules have been proposed as an ideal model system to explore novel physical phenomena at the intersection of molecular physics with few- and many-body quantum physics
The most interesting relative alignments that characterize two different physical regimes based on the barrier height are obtained for θ = 0◦ and θ = θc ≈ 20◦, where θc is the angle for which the barrier dips below the asymptotic threshold
We theoretically investigated photoassociative production of cold tetratomic molecules, and potentially larger polyatomic molecules, from pairs of ultracold polar molecules
Summary
Ultracold polar molecules have been proposed as an ideal model system to explore novel physical phenomena at the intersection of molecular physics with few- and many-body quantum physics. They could be used to engineer and study lattice spin models in strongly interacting manybody Hamiltonians [1,2,3,4,5,6], supersolidity [7], unconventional superfluid phases and quantum magnetism [8,9], to name a few. Unlike atomic gases, where inter-particle interactions are isotropic and shortrange, gases of ultracold polar molecules exhibit much richer dynamics and macroscopic properties due to the long-range anisotropic electric dipole-dipole interactions between their constituents.
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