New class of materials could power memory devices

A new phase of matter known as topological insulators, until recently known only for esoteric quantum-mechanical properties, might have a practical use in controlling magnetic memory and logic devices. A team of Cornell and Penn State University physicists has demonstrated for the first time that electrical currents flowing along the surface of topological insulators can exert a torque on an adjacent magnetic layer that is 10 times more efficient than any other known mechanism. This breakthrough provides a new strategy for making next-generation memory technologies that use the least possible energy and current. The research, led by Dan Ralph, the F.R. Newman Professor of Physics at Cornell, and Nitin Samarth of Penn State, is published online July 24 . The team used the topological insulator bismuth selenide (a combination of bismuth and selenium) for their experiments. Like conventional insulators, topological insulators do not allow current to flow through the material, but they are different because they are wrapped in a conducting surface. Electrons flowing on the surface also do something unique: The direction of an electron's spin is always locked perpendicular to its direction of motion.