Understand Supersolidity with a review and video

A supersolid is a spatially ordered material (that is, a solid or crystal) with superfluid properties. Superfluidity is a special quantum state of matter in which a substance flows with zero viscosity (or resistance to flow). Liquid helium-4 has long been known (since the work of Peter Kapitza, John F. Allen, and Don Misener, published in 1938 the Journal Nature 141, 74 and 75) to exhibit this property when it is cooled below a characteristic transition temperature called the lambda point Tλ. Also superfluidity is observed when superconductors are cooled below a critical temperature Tc. However, before the recent observation of supersolid-like behavior in solid helium-4, superfluidity was considered to only be a property of electron fluids, such as in superconductors; gases, such as dilute alkali gases; or liquids, such as liquid helium-4 or liquid helium-3 at very low temperature.Superfluidity in helium arose from the normal liquid by a second-order phase transition ("lambda transition"). In a dilute gas of Bose particles it comes about by a phase transition that belongs to the universality class of the spherical model. In thin liquid helium films it arises from the normal liquid by a Kosterlitz-Thouless transition.[...]

• How Helium Can Be Solid And Perfect Liquid At Same Time, Now Explained By Computer-assisted Physics: At very low temperatures, helium can be solid and a perfect liquid at the same time. Theoreticians, though, have incorrectly explained the phenomenon for a long time. Computer simulations have now shown that only impurities can make this effect possible.[1]
• Major Physics Breakthrough In Understanding Supersolidity: Physicists are reporting a major advance in the understanding of what appears to be a new state of matter -- supersolidity. Physicists have been manipulating solid helium so they can study its unusual behavior.[2]

Watch a video on Rotating supersolid helium

• When Is A Supersolid Not Quite So Super? Brown University physicist Humphrey Maris and colleagues Satoshi Sasaki and Sebastien Balibar of the l'Ecole Normale Supérieure have narrowed the field of possible explanations for the weird behavior of supersolid helium. Their simple but extremely revealing experiment suggests that movement along grain boundaries is a more plausible explanation than Bose-Einstein condensates.[3]
• Probable Discovery Of A New, Supersolid, Phase Of Matter: In the 15 January 2004 issue of the journal Nature, two physicists from Penn State University will announce their discovery of a new phase of matter, a "supersolid" form of helium-4 with the extraordinary frictionless-flow properties of a superfluid.[4]
• Supersolids -- Can Atoms Unify And Flow Without Resistance?: Imagine you have an orchestra together, but everyone is playing their own tune, until they begin to follow a conductor. In a normal solid, every atom has its own behavior until very close to absolute zero. Then quantum mechanics takes over and dictates everyone to play the same tune.[5]