How Atoms Themselves Create a Mosaic That Never Repeats ⚡ экспресс
Researchers explored a mixture of two Bose–Einstein condensates in a twisted spin-dependent optical lattice. With equal particle numbers, cranking up repulsion between the components shifts the system from ordinary fourfold symmetry to eightfold — a quasicrystal (a nonperiodic yet symmetric pattern). The twist: at moderate interactions, order vanishes due to phase separation, but at strong interactions it reappears as a long-lived metastable state with new momentum rings. For an imbalanced mixture, quasicrystals don’t survive. Simulations confirm that population balance is the key to stabilizing quantum quasicrystals, and they are experimentally observable.
Ordinary tiles form a repeating pattern. But atoms can do more: under certain conditions, they themselves lay out a complex mosaic where the pattern never repeats, like on antique tile panels.
In a recent experiment, two types of atoms cooled to a joint wave state (a phenomenon predicted by Einstein) were trapped in a crosshatch of laser beams. When their mutual repulsion became strong, glow observations and pulse measurements revealed a pattern with eightfold symmetry. This is a hallmark of a quasicrystal — a structure with order but no repetition, unlike a crystal lattice.
An ordinary crystal, like wallpaper, consists of identical cells. A quasicrystal is more like a mosaic where no fragment repeats exactly, but the overall design is harmonious. The stability of such an atomic mosaic requires equal numbers of both types of atoms. The slightest imbalance destroys the pattern. From the standpoint of a measure of disorder, the system first loses regularity but then finds a more sophisticated packing scheme. Most surprising: such patterns, once considered a mathematical abstraction, were first discovered in meteorite material, and now they are created in the lab using only light and cold.
🎯 Eightfold symmetry is forbidden for ordinary crystals, so quasicrystals, first produced in 1982, became a scientific sensation. Later such structures were found in meteorites, showing that nature can create the impossible.