supersolid
A supersolid is a phase of matter that combines the rigid, periodic structure of a crystal with the frictionless flow characteristic of a superfluid. In a supersolid, atoms maintain a crystalline lattice while a portion of the material participates in coherent, dissipationless motion typically associated with superfluidity.
The concept originated in theoretical discussions in the 1960s by Andreev, Lifshitz, and Chester, who proposed
Experimental searches in solid helium-4 produced initial reports of non-classical rotational inertia, suggestive of supersolidity, but
More robust realizations have emerged in ultracold atomic gases, where density modulations with preserved phase coherence
Today, supersolidity is an active area of research. In helium, the existence of a bulk supersolid is