To Cory Dean, Avik Ghosh and colleagues at Columbia University, the University of Virginia, Cornell University, the Japanese National Institute for Materials Science, Shenyang National Laboratory for Materials Science and IBM for measuring the negative refraction of electrons in graphene. Negative refraction is a property of some artificial metamaterials and can be used to create novel optical devices such as a perfect lens. Electrons in materials can behave as waves and negative refraction should also occur at the interface between an n-type and a p-type semiconductor (a p-n junction). It has proven impossible to see this effect in conventional semiconductors because most electrons are reflected at p-n junctions. Dean and colleagues created a p-n junction in graphene and ensured that the interface was very smooth to minimize reflections - allowing them to measure the negative refraction of electrons. Negative refraction could be used to bring a diverging electron beam to a sharp focus and this could form the basis of an electronic switch that consumes very small amounts of energy. See the complete list.