17-22 July 2022
Royal Conservatory of Music, Toronto
America/Toronto timezone

Realization of a ferromagnet in an atomic superfluid

19 Jul 2022, 17:00
1h 30m
Hart House (Hart House)

Hart House

Hart House

7 Hart House Cir, Toronto, ON M5S 3H3
Poster presentation Degenerate gases, many-body physics, and quantum simulation Poster session


Interactions in materials characterized by spin degrees of freedom play a crucial role in determining the magnetic properties both in the presence and in the absence of an external coherent drive. For instance, if the spin-dependent interaction is positive and strong as compared to the external drive the material behaves as a ferromagnet, otherwise it shows a paramagnetic response to external perturbations.

By means of accurate control of the spin degrees [1,2], and of polarization-resolved spatial imaging in a coherently-driven 23Na Bose-Einstein condensate we explore the magnetic phase diagram of an extended superfluid. In the limit of strong external driving or small spin-dependent interaction (low density) the system features a paramagnetic response whereby the polarization is determined by the frequency detuning of the drive, while in the opposite limit of strong spin interaction the systems shows typical ferromagnetic behaviour with hysteresis, formation of magnetic domain walls, and divergent magnetic susceptibility.

Using a similar experimental setup we perform complementary measurements of the spin dispersion relation of a two-component superfluid demonstrating the massive (gapped) character of collective excitations when the superfluid is subject to stationary resonant driving [3], and of the role of quantum torque under strongly nonstationary driving [4].

[1] A. Farolfi et al., Rev. Sci. Instrum. 90, 115114 (2019).
[2] A. Farolfi et al., Phys. Rev. A 104, 023326 (2021).
[3] R. Cominotti et al., Phys. Rev. Lett. 128, 210401 (2022).
[4] A. Farolfi et al., Nat. Phys. 17, 1359 (2021).

Presenter name Gabriele Ferrari
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