Editors' ChoicePhysics

An elusive magnet in an atomic cloud

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Science  12 May 2017:
Vol. 356, Issue 6338, pp. 595-596
DOI: 10.1126/science.356.6338.595-d

Whether repulsive interactions alone can cause a system of electrons to become ferromagnetic is an open problem in condensed matter physics. One way to tackle it is to use cold fermionic atoms of opposite spins instead of electrons and generate interactions by tuning an external magnetic field. However, such atoms are much more likely to form a superfluid than a ferromagnet. To avoid the superfluid pairing, Valtolina et al. started with an atomic system divided neatly into two clouds of opposite spin, with a barrier separating them. After removing the barrier, they monitored the dynamics of the cloud motion and the spin diffusion. For some interaction strengths, the dynamics were consistent with those of a metastable ferromagnetic state.

Nat. Phys. 10.1038/NPHYS4108 (2017).

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