A fluid of tiny magnets

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Science  20 Jul 2018:
Vol. 361, Issue 6399, pp. 241-242
DOI: 10.1126/science.361.6399.241-f

One of the most fascinating phenomena in many-body systems is the emergence of so-called collective modes, where the constituents of the system start acting in sync. Lepoutre et al. revealed such behavior in an ultracold gas of chromium atoms, which carry a large magnetic moment. The researchers first coaxed the atoms' spins to align along a direction perpendicular to an external magnetic field, which had a small gradient. The gradient acted to couple the atoms' spin and spatial degrees of freedom, resulting in a collective mode in which the spins oscillated with an amplitude that was dependent on their position. The experimental results were consistent with a hydrodynamic model.

Phys. Rev. Lett. 121, 013201 (2018).

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