Probing coherences and itinerant magnetism in a dipolar lattice gas made of magnetic chromium atoms

I will report on the study of itinerant magnetism of lattice-trapped chromium atoms, driven by magnetic dipole-dipole interactions, in the low-entropy and close-to-unit filling regime. We have used advanced dynamical decoupling techniques to efficiently suppress the sensitivity of the system to magnetic field fluctuations. Thanks to this effort, we have extended the spin coherence time by roughly three orders of magnitude.

We have thus measured the spin coherence of an itinerant spin 3 Bose dipolar gas throughout a quantum phase transition from a superfluid phase to a Mott insulating phase. In the superfluid phase, a metastable ferromagnetic behavior is observed below a dynamical instability which occurs at lattice depths below the phase transition. In the insulating phase, the thermalization towards a paramagnetic state is driven by an interplay between intersite and superexchange interactions.

I will present our experimental results as well as perturbative and effective-model approaches that capture the role of both contact and dipolar interactions in determining spin coherence in the itinerant regime.