For years, physicists have wondered why metals, which are so good at conducting electricity, lose that ability when they are made in ultrathin films. But a recent paper in Nature suggests a surprising answer that delves into the quantum realm. Most scientists sought a solution by first creating a thin film from vaporized metals and then testing the films for conductivity. Inevitably, they found poor conductivityprobably because the vapors of most metals fall in droplets and make a granular film, says Philip W. Adams of Louisiana State University.

Adams and postdoctoral researcher Vladimir Y. Butko approached the problem in a slightly different way. They discovered that vaporized beryllium makes a smooth film, and that it, too, did not conduct electricity very welluntil they applied a magnetic field. As they increased the magnetic field, the beryllium's resistance fell, until finally it stabilized at what is known as the quantum resistance. The find was especially surprising because beryllium is not magnetic, but the researchers suspect that all metals behave in this way. The significance, Adams says, is that there is a universal standard for limiting a metal film's resistance to conductivity.