All Paired Up but Unable to Flow, Atoms Strain Key Conceptual Link

摘要

Day leads to night, life leads to death, win-ter leads to spring; some things necessarily imply others. So it has seemed in physics: At very low temperatures, certain particles pair, and when they do, the pairs inevitably gang up to form a "superfluid" that flows without resistance. That explains how electrons glide through superconductors, how atoms of helium-3 form a liquid with no viscosity, and perhaps, how neutrons circulate through neutron stars. But an experiment reported on page 867 breaks the pairing-to-superfluidity connection. Atoms in an ultra-cold gas can pair but do not flow without resistance, even at temperatures approaching absolute zero, physicists report.