Strongly magnetic spinor bose gases under control

Ultracold lanthanides are ideal systems to realise large-spin quantum systems with long-range interactions because of their rich electronic structure and large magnetic moment. However, to study quantum magnetism and spin-lattice models, the ability to prepare any spin state in a controlled, deterministic and fast manner is required.

Here we showcase a novel way of manipulating the spin degree of freedom by means of a laser tuned to a clock-like transition present in Erbium at 1299nm. Mixtures of arbitrary Zeeman levels are created by applying a series of pulses with different polarisation. In these mixtures, new Feshbach resonances have been observed, which can be used as benchmarks for quantum scattering calculations and as a tool to tune inter- and intraspecies contact interactions.

Furthermore, we show that spin-exchange, mediated by strong dipole-dipole interactions in erbium, can be turned off at will using AC-Stark shifts generated by the same laser. This effectively adds the possibility to limit the spin dynamics to subsets of the complete spin-manifold.