By taking two flakes of special materials that are just one atom thick and twisting them at high angles, researchers at the University of Rochester have unlocked unique optical properties that could be used in quantum computers and other quantum technologies. In a new study published in Nano Letters , the researchers show that precisely layering nano-thin materials creates excitons—essentially, artificial atoms—that can act as quantum information bits, or qubits.
"If we had just a single layer of this material we're using, these dark excitons wouldn't interact with light," says Nickolas Vamivakas , the Marie C. Wilson and Joseph C. Wilson Professor of Optical Physics. "By doing the big twist, it turns on artificial atoms within the material that we can control optically, but they are still protected from the environment."
Moiré is less
The work builds on the 2010 Nobel Prize–winning discovery that peeling carbon apart until it reaches a single layer of atoms creates a new two-dimensional (2D) material called graphene with special quantum characteristics.
Scientists have since explored how optical and electrical properties of graphene and other 2D materials change when layered on top of one another and twisted at very small angles—called moiré superlattices. For example, when graphene is twisted at the "magic" angle of 1.1 degrees, it creates special patterns that produce properties such as superconductivity.
But scientists from Rochester's Institute of Optics and Department of Physics and Astronomy took a different approach. They used molybdenum diselenide, a 2D material that is more fickle than graphene, and twisted it at much higher angles of up to 40 degrees. Still, the researchers found the twisted monolayers produced excitons that were able to retain information when activated by light.
"This was very surprising for us," says Arnab Barman Ray, an optics PhD candidate. "Molybdenum diselenide is notorious because other materials in the family of moiré materials show better information-retaining capacity. We think that if we use some of those other materials at these large angles, they will probably work even better."
The team views this as an important early step toward new types of quantum devices.
"Down the line, we hope these artificial atoms can be used like memory or nodes in a quantum network, or put into optical cavities to create quantum materials," says Vamivakas. "These could be the backbone for devices like the next generation of lasers or even tools to simulate quantum physics."
The research was supported through the Air Force Office of Scientific Research and conducted at the URnano facilities .
