Preparation of the Spin-Mott State: A Spinful Mott Insulator of Repulsively Bound Pairs.

We observe and study a special ground state of bosons with two spin states in an optical lattice: the spin-Mott insulator, a state that consists of repulsively bound pairs that is insulating for both spin and charge transport. Because of the pairing gap created by the interaction anisotropy, it can be prepared with low entropy and can serve as a starting point for adiabatic state preparation. We find that the stability of the spin-Mott state depends on the pairing energy, and observe two qualitatively different decay regimes, one of which exhibits protection by the gap.

Tunable Single-Ion Anisotropy in Spin-1 Models Realized with Ultracold Atoms.

Mott insulator plateaus in optical lattices are a versatile platform to study spin physics. Using sites occupied by two bosons with an internal degree of freedom, we realize a uniaxial single-ion anisotropy term proportional to (S^{z})^{2} that plays an important role in stabilizing magnetism for low-dimensional magnetic materials. Here we explore nonequilibrium spin dynamics and observe a resonant effect in the spin alignment as a function of lattice depth when exchange coupling and on-site anisotropy are similar. Our results are supported by many-body numerical simulations and are captured by the analytical solution of a two-site model.

Control of quantum dot emission by colloidal plasmonic pyramids in a liquid crystal.

We study the plasmon-enhanced fluorescence of a single semiconducting quantum dot near the apex of a colloidal gold pyramid spatially localized by the elastic forces of the liquid crystal host. The gold pyramid particles were manipulated within the liquid crystal medium by laser tweezers, enabling the self-assembly of a semiconducting quantum dot dispersed in the medium near the apex of the gold pyramid, allowing us to probe the plasmon-exciton interactions. We demonstrate the effect of plasmon coupling on the fluorescence lifetime and the blinking properties of the quantum dot. Our results demonstrate that topological defects around colloidal particles in liquid crystal combined with laser tweezers provide a platform for plasmon exciton interaction studies and potentially could be extended to the scale of composite materials for nanophotonic applications.