Topological insulators are materials that are electrical insulators in the bulk but can conduct electricity on their surface via special surface electronic states. Using just a couple of diagrams on a whiteboard, Chris Hooley of the University of St Andrews in the UK shows how this phenomenon arises from the presence of electrons and their spin properties.

The unusual properties of these materials has generated a lot of interest in the condensed-matter community in recent years. They bring a great opportunity to expand our understanding of materials physics and could lead to applications such as quantum computation.

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