In a paper recently published on Nature Physics, we show that strong repulsive interactions alone are sufficient to temporarily stabilize ferromagnetic correlations in an ultracold Fermi gas. We study the collective spin dynamics of an ultracold lithium spin mixture, artificially engineered in a fully ferromagnetic state, obtained by spatially segregating oppositely-oriented spins into two adjacent reservoirs. In particular, we reveal a substantial increase of the magnetic susceptibility of the gas while approaching the critical value of the atomic interaction strength. We directly show that above the critical interaction a spin up-down domain wall can persist for a finite amount of time, indicating the metastability of the ferromagnetic state.
The experimental study has been carried out by the INO-CNR researchers in the ultracold lithium laboratory in Sesto Fiorentino led by Giacomo Roati, in collaboration with the theoretical researchers Alessio Recati from the INO-CNR BEC Center in Trento and Tilman Enss from the University of Heidelberg.

G. Valtolina, F. Scazza, A. Amico, A. Burchianti, A. Recati, T. Enss, M. Inguscio, M. Zaccanti & G. Roati, “Exploring the ferromagnetic behaviour of a repulsive Fermi gas through spin dynamics”, Nature Phys. 13, 704-709 (2017).

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