Say ‘Hello’ to the STEM Field of the Future: Twistronics

In 2018 a lab at MIT rocked the physics world when they showed that they could achieve superconductivity—the flow of electricity without resistance—in a new way. They did it by layering two sheets of graphene and rotating the top one by about 1.1 degrees. The discovery set off an explosion of research in a new field: “twistronics.”

Researchers at the Advanced Science Research Center at The Graduate Center, CUNY, and colleagues in Texas, Singapore, Australia, and China took this idea and approached it from a different direction. They asked how this “magic angle” of rotation could affect the transmission of light rather than electricity.

In a paper published in Nature, Professors Andrea Alù and Alex Krasnok of CUNY ASRC and colleagues reported that they are able to use ideas from twistronics to create a tightly-controlled beam of light that doesn’t diffract, and can do so for a range of different wavelengths. Their insights could lead to advancements in nano-imaging, biosensing, and high-speed, low-energy optical computers.

The researchers used molybdenum trioxide, a compound that occurs naturally as a mineral and is used in steel production. In the new study, the scientists took two flakes of molybdenum trioxide and layered one on top of the other. By rotating the top flake with respect to the bottom one, they found they could control the transmission of light across the material.

At the same magic angle of rotation that the MIT lab used to produce superconductivity, the ASRC researchers produced a beam of light without any diffraction. Diffraction is the bending of light waves as they go around an object or through a hole, so preventing diffraction creates a much more tightly focused beam.

“We have observed dramatic control of the light guiding properties,” Alù told CUNY ASRC. “At the photonic magic angle, light does not diffract, and it propagates very confined along straight lines. This is an ideal feature for nanoscience and photonic technologies.”