Symmetry breaking is routinely observed in isolated systems, where perturbations propagate through the system. For out-of-equilibrium systems, however, perturbations are predicted to diffuse; and this key signature of spontaneous symmetry breaking has now been observed in a polariton quantum fluid.
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This is a summary of: Claude, F. et al. Observation of the diffusive Nambu–Goldstone mode of a non-equilibrium phase transition. Nat. Phys. https://doi.org/10.1038/s41567-025-02902-z (2025).
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Perturbations in out-of-equilibrium quantum fluids diffuse rather than propagate. Nat. Phys. 21, 879–880 (2025). https://doi.org/10.1038/s41567-025-02913-w
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DOI: https://doi.org/10.1038/s41567-025-02913-w
