A superfluid freezes and breaks the rules of physics
In a sheet of graphene, a superfluid has finally frozen—revealing a long-mysterious quantum state that blurs the line between solid and liquid.
When everyday matter is cooled, it follows a familiar path. A gas becomes a liquid, and with further cooling, that liquid turns into a solid. Quantum matter does not always follow these rules. More than a century ago, scientists discovered that helium behaves in an unexpected way at extremely low temperatures. Instead of freezing, it transforms from a normal gas into a superfluid, a rare state of matter that flows without any resistance and displays strange behaviors, including creeping up the sides of containers. Physicists have long wondered what would happen if a superfluid were cooled even further. Despite decades of effort, that question remained unanswered for nearly 50 years.
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