U.S. researchers engineered new types of particles called 'topological plexcitons' to help make energy transfer in solar cells and other forms of photonic circuits more efficient.

Biochemist Joel Yuen-Zhou stated "energy can flow back and forth between light in a metal (so-called plasmon) and light in a molecule (so-called exciton)." Yuen-Zhou added that if the exchange is much faster than the decay rates, their individual identities of excitons and plasmons are lost, making them hybrid particles called plexcitons.

Two For the Power of One

Physicists from the UC San Diego, the Massachusetts Institute of Technology (MIT), and Harvard University have used materials called topological insulators to act as conductors for exciton energy transfer (EET), forcing the plexcitons to move in one direction. This allowed scientists to control the flow of light energy at an incredibly small scale.

Plexcitons travel for 20,000 nanometers, a length which is on the order of the width of human hair. Graphic by Joel Yuen-Zhou

The Future of Nanoelectronics

Plexcitons extend the range of EETs but the energy flow is very difficult to harness, which is where this new research comes in. "The exciting feature of topological insulators is that even when the material is imperfect and has impurities, there is a large threshold of operation where electrons that start traveling along one direction cannot bounce back, making electron transport robust," said Yuen-Zhou. "In other words, one may think about the electrons being blind to impurities."

The research could enable engineers to create 'plexcitonic switches' that can distribute energy selectively across solar panels or other kinds of light-harvesting devices. The plexcitons are deemed to be crucial in the development of light-based nanoelectronics in the future, so being able to control them in this way could be a significant step forward.

If all of this research becomes successful, these topological plexcitons could replace silicon circuits, and end up in our future tech devices.

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