To Condense or Not to Condense

Bosonic particles choose between a classical crystalline or a Bose-Einstein condensed ground state depending on the strength of their interactions. In his Perspective, Rice explains how this competition can be observed in quantum magnets composed of spin-dimer arrays when a magnetic field is applied. This generates spin triplet bosons with a tunable density. Magnetization plateaus correspond to spatially ordered arrays of the spin triplets. The detailed structure of such an array has been unraveled in a recent NMR experiment.