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Spontaneous pattern formation in an anti-ferromagnetic quantum gas

Spontaneous pattern formation is a phenomenon ubiquitous in nature, examples ranging from Rayleigh-Benard convection to the emergence of complex organisms from a single cell. In physical systems, pattern formation is generally associated with the spontaneous breaking of translation symmetry and is closely related to other symmetry-breaking phenomena, of which (anti-)ferromagnetism is a prominent example. Indeed, magnetic pattern formation has been studied extensively in both solid-state materials and classical liquids. Here, we report on the spontaneous formation of wave-like magnetic patterns in a spinor Bose-Einstein condensate, extending those studies into the domain of quantum gases. We observe characteristic modes across a broad range of the magnetic field acting as a control parameter. Our measurements link pattern formation in these quantum systems to specific unstable modes obtainable from linear stability analysis. These investigations open new prospects for controlled studies of symmetry breaking and the appearance of structures in the quantum domain.