Physicists have harnessed the aloofness of quantum particles to create a new type of crystal.

Some particles shun one another because they are forbidden to take on the same quantum state as their neighbors. Atoms can be so reluctant to overlap that they form a crystal-like arrangement even when they aren’t exerting any forces on one another, physicists report May 8 at Called a Pauli crystal, the configuration is the result of a quantum mechanical rule called the Pauli exclusion principle.

Scientists had previously predicted the existence of Pauli crystals, but no one had observed them until now. “It just teaches us how beautiful physics is,” says quantum physicist Tilman Esslinger of ETH Zurich. The experiment reveals there are still new phenomena to be observed from a foundational principle taught in introductory physics classes. “If I wrote a textbook,” Esslinger says, “I would put that [experiment] in.”

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