The frictionless flow of atoms within solid helium may be confined to the axis of a screw dislocation, a spiral defect like the one in this crystal of silicon carbide.
Image Credit: Gunter Wagner/Institute for Crystal Growth, Germany
The strange quantum phenomenon known as supersolidity occurs when atoms flow without friction through a solid block of helium, possibly along a network of defects extending through an otherwise perfect crystal. Recently, physicists have found such a flow in computer simulations even when the atoms that make up the defects form a regular pattern, unlike the disorderly arrangement used in previous calculations. The results open a new way of understanding this extraordinary state of matter, which has properties of both solids and liquids.