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Electron spin converted to light

Researchers from the Kavli Institute of Nanoscience at TU Delft, working with the Netherlands Organisation for Scientific Research, have found a way to convert spin information in electrons into a predictable light signal at room temperature. The discovery is said to bring the worlds of spintronics and nanophotonics closer together and to hold the prospect of an energy-efficient way of processing data.

The work focuses on two components – an extremely thin silver thread, and the 2D material tungsten disulphide (WS2). The silver thread was attached to a four atom thick slice of WS2 and, using circularly polarised light, the team created ‘excitons’ with a specific rotational direction initialised using the laser’s rotational direction.

Excitons are electrons that have been ‘bounced’ out of their orbit. When they return to their original state, they emit light which not only contains the spin information, but is also emitted in all directions.

The Delft team had already shown that when light moves along a nanowire, it is accompanied by a rotating electromagnetic field locked to the direction in which light travels along the wire. “We use this phenomenon as a type of lock combination,” said TU Delft Professor Kobus Kuipers. “An exciton with a particular rotational direction can only emit light along the thread if the two rotational directions correspond.”

According to the researchers, the technique, which works at room temperature, could enable new optoelectronic circuitry. Prof Kuipers noted: “You don’t need a stream of electrons and no heat is released. This makes it a very low-energy way of transferring information. This combination may well result in green information processing strategies at the nanoscale.”

Author
Graham Pitcher

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