Relaxation of the collective magnetization of a dense 3D array of interacting dipolar S = 3 atoms

We report on measurements of the dynamics of the total magnetization and spin populations in an almost unit-filled lattice system comprising about 10^4 spin 𝑆 =3 chromium atoms, under the effect of dipolar interactions.
arXiv:2005.13487 (2020) / Phys. Rev. Lett. 125, 143401 (2020)

The observed spin population dynamics is unaffected by the use of a spin echo and fully consistent with numerical simulations of the 𝑆 =3 𝑋⁢𝑋⁢𝑍 spin model. On the contrary, the observed magnetization decays slower than in simulations and, surprisingly, reaches a small but nonzero asymptotic value within the longest timescale.

Our findings show that spin coherences are sensitive probes to systematic effects affecting quantum many-body behavior that cannot be diagnosed by merely measuring spin populations.

The experimental system consists of a 3D array of dipolar Cr atoms, with a spatially varying magnetic field B(r). Experimental RF sequence: Cr atoms are initialized in the ms = −3 spin state and rotated by the first π/2 pulse to align with the x direction; the 2nd π/2 pulse is used to measure the spin length.