Matthias Wuttig

A light beam inscribes a pattern on a thin crystal, and heat runs along that pattern in the desired direction, like water along a dug channel. This is how the new method works to control energy flows over distances of tens of nanometers — hundreds of times thinner than a human hair.

A stack of playing cards lies still. You can slide the top card with your finger: that's crude intervention. Or you can blow so that the whole stack momentarily changes shape, but the cards don't scatter. That's roughly how light, in a new experiment, rearranges a crystal of tin selenide (SnSe). Usually, to change the structure of a solid, you heat it or pass a current through it.