In planar materials like graphene, light-like electrons must always come in pairs (even number of cones). By directly imaging the spinning of electrons confined to the surfaces of special materials, an international team of scientists led by Princeton University have now shown the existence of a new type of strange quantum matter in nature called 'topological insulators', which contain only half an electron pair or just one cone. This is observed in the form of a single ring in the center of the electron-map data with particles spinning around only in one direction. This highly unusual observation shows that if an electron is tagged 'red' and then undergoes a full 360 degree revolution about the ring, it does not recover its initial face as an ordinary everyday object would do, but instead acquires a different color 'blue'. The researchers have shown that this new quantum effect can be the basis for the realization of a rare quantum phase or the 'color' of the electron, which had been a long-sought key ingredient for developing quantum computers that can correct themselves.

Credit: Zahid Hasan

Feb. 13, 2009 cover of the journal Science.

Credit: Copyright 2009 AAAS