Lasers and ions provide insight into superlubricity

Nature : Atomic force microscopes have been used to measure friction of individual atoms within larger surfaces, but they don’t have the ability to measure that of solitary atoms. Now Vladan Vuletić of MIT and his colleagues have developed a technique that allows them to measure the forces on isolated atoms. They created one surface from a line of ytterbium atoms held in place by an electric field. For the second surface—or, rather, the forces it exerts on the first surface—they formed an interference pattern of overlapping lasers. The researchers could then measure the force between the two surfaces by sliding the line of ytterbium atoms across the ridged interference pattern. And as they increased the spacing between the atoms, they saw a 10-fold decrease in that force, which mimicked the drastic decrease in friction known as superlubricity.