Ann Arbor Times

Engineers at the University of Michigan have developed a new nanostructure that can control and direct the flow of excitons, which are quantum quasiparticles, at room temperature. This development could lead to faster information transfer and potentially circuits that operate on excitons instead of electricity.

Excitons do not carry an electrical charge, so they may move quantum information without the energy losses associated with electrons. These losses are responsible for heat generation in electronic devices such as cell phones and computers.

“You can see the limits of electronics being reached now with AI and other demanding computations consuming energy and generating heat like crazy. If large processing centers were instead powered by excitonics, you wouldn’t have this huge energy consumption anymore,” said Mack Kira, co-corresponding author of the study in ACS Nano, supervisor of the theory and a professor of electrical and computer engineering.

Excitons are already used in various applications including lights and solar cells. The research was partly funded by the U.S. Army Research Office and U.S. Air Force Office of Scientific Research.

“Our cell phone displays work using organic LEDs, which are all excitonic-based,” said Parag Deotare, co-corresponding author, supervisor of the experimental work and an associate professor of electrical and computer engineering. “Plants even convert light into excitons for photosynthesis, then transport that quantum energy packet to where it is needed before converting it into chemical energy.”

Excitons form when an electron in a semiconductor is excited to a higher state, leaving behind a positively charged hole; together they move as a neutral pair. While their neutral charge allows for movement without loss, it also makes them difficult to control deliberately since conventional electrodes cannot direct them as easily as charged particles.

To address this challenge, researchers designed an energy landscape to guide excitons along a ridge structure similar to a wire. Electrodes placed on either side act as gates that control whether excitons can pass.

“When the electrodes are switched on, the voltage creates an energy barrier that prevents the excitons from moving. When the voltage is switched off, the excitons flow again. A switch like this has not been done up to this point,” said Zhaohan Jiang, U-M doctoral student of electrical and computer engineering and lead author of the study.

Testing showed that the device achieved an on-off switching ratio exceeding 19 decibels—sufficient for advanced optoelectronic uses such as high-speed data transfer links used in supercomputers, data centers, AI-enabled smartphones and wearables, autonomous vehicles, digital twins and more.

The device also uses light both to generate excitons by exciting electrons and to help drive them along the ridge structure—a method described as ‘optoexcitonic.’ The combination allowed successful one-way transport over distances up to 4 micrometers in less than half a nanosecond at room temperature.

Looking ahead, researchers plan to connect multiple switches together for more complex circuits.

“While this technology could become an optoexcitonic circuit as it matures, I see it first improving the interface between photonics and electronics which will speed up processing and communication,” Deotare said.

Such technology could help meet growing demand for rapid data transmission in areas such as data centers or artificial intelligence applications.

The team has filed for patent protection through U-M Innovation Partnerships. The device was fabricated at the Lurie Nanofabrication Facility with simulations run using resources from U-M Advanced Research Computing; both facilities receive support from federal grants allocated indirectly through cost recovery mechanisms.