Whereas bosons can condense into a single quantum state, fermions, such as electrons in ordinary solids, are forbidden from doing so. Pauli exclusion is the best-known manifestation of Fermi–Dirac statistics, and it accounts for, among other things, the structure of the periodic table and electrical conductivity in metals.
Identical fermions do not even need to interact to behave as if they repel each other. Indeed, the mere presence of fermionic atoms near one another but unable to occupy the same locations produces an emergent Fermi pressure that prompts the atoms to rearrange themselves. The resulting correlations between atoms can be visualized in geometric structures known as Pauli crystals. Mariusz Gajda coined the name five years ago when he and his colleagues at the Polish Academy of Sciences in Warsaw predicted the phenomenon.1
Now doctoral student Marvin Holten, postdoc Luca Bayha, and their colleagues, under the direction of Selim Jochim...
