A Slippery New State of Matter

Physicists Moses Chan and Eun-Song Kim of Pennsylvania State University report they have created a supersolid, a frictionless phase of matter in which atoms behave more like a unified wave than separate particles. If so, the supersolid would complete Albert Einstein and Satyendra Bose’s 1924 theory that such “super” phases exist in solids, liquids, and gases. Researchers have already found super liquids and vapors. Chang and Kim cooled liquid helium to a fraction of a degree above absolute zero and compressed it at 900 pounds per square inch. The helium became a solid whose atoms settled into the same quantum ground state, meaning they had all the same energy. In this phase, called a Bose-Einstein condensate, the wavelike aspects of matter become prominent. As the waves of the atoms overlap, millions of them move as a single ripple “like soldiers marching in formation.” Atoms in this state don’t collide and therefore don’t create any friction. Chan believes the discovery of supersolid matter could have a far-reaching impact on theoretical physics: “Physicists intuitively thought that Bose-Einstein condensation could not happen in a solid. Our experiment has removed that boundary,” he says. The realization could lead to new insights into superconductivity and exotic astrophysical objects such as neutron stars.