Scientists bent graphene nearly to atomic limits and observed unusual effects

Researchers have observed a novel electrical phenomenon in graphene, a material renowned for its strength, conductivity, flexibility, and lightness. The study, conducted by teams in the US and UK, found that sharp bends in graphene can alter its local electrical potential, aligning with theoretical predictions made in 2008. This discovery could pave the way for ultrathin electronic devices utilizing graphene's unique properties without additional materials.

The phenomenon, known as flexoelectricity, occurs when uneven bending causes a separation of electrical charge. In graphene, which is only one atom thick, these extreme bends affect electron orbitals, leading to what researchers term quantum orbital flexoelectricity. This effect changes how electrons are distributed around the wrinkle, offering new insights into the material's electronic behavior.

Sathvik Ajay Iyengar, a former doctoral student at Rice University, identified unusual electrical signals in graphene wrinkles during his research with Manoj Tripathi. These findings were linked to earlier theoretical work by Vincent Meunier, who had predicted electronic flexoelectricity in low-dimensional systems like graphene. The wrinkles appeared where graphene rested on molybdenum disulfide, another atomically thin material, due to differing mechanical stress responses.

The study highlighted that the sharpness of the graphene wrinkles was more critical than their height in influencing electrical behavior. At the sharpest points, electrons shifted significantly, creating a pronounced electrical imbalance. This polarization was found to be 100,000 to 10 million times stronger than in larger flexoelectric systems.

The implications of this discovery suggest that engineers could potentially control the behavior of atomically thin electronics by manipulating the curvature of materials like graphene. However, challenges remain, as accurately measuring the smallest bends and constructing practical devices around this effect are yet to be achieved. The research was published in the journal Advanced Materials.