A superfluid freezes and breaks the rules of physics

Physicists have watched a quantum fluid do something once thought almost impossible: stop moving. In experiments with ultra-thin graphene, researchers observed a superfluid—normally defined by its endless, frictionless flow—freeze into a strange new state that looks solid yet still belongs to the quantum world. This long-sought phase, known as a supersolid, blends crystal-like order with superfluid behavior and has puzzled scientists for decades.