Researchers at MIT have succeeded in producing and measuring a coupling of photons and electrons on the surface of an unusual type of material called a topological insulator. This type of coupling had been predicted by theorists, but never observed.

The researchers suggest that this finding could lead to the creation of materials whose electronic properties could be “tuned” in real time simply by shining precise laser beams at them. This work opens up a new avenue for optical manipulation of quantum states of matter.

The MIT researchers’ method involves shooting femtosecond (millionths of a billionth of a second) pulses of mid-infrared light at a sample of material and observing the results with an electron spectrometer, a specialized high-speed camera the team developed.

It opens new avenues not only for optical control of topological states, but also more generally for engineering of new kinds of electronic states in solid-state systems.

Their findings suggest that it’s possible to alter the electronic properties of a material — for example, changing it from a conductor to a semiconductor — just by changing the laser beam’s polarization.

For example, a property called a bandgap — a crucial characteristic for materials used in computer chips and solar cells — can be altered by shining a polarized laser beam at the material.