Science: Ultrafast Imaging of Electron Waves in Graphene
The fastest movies ever made of electron motion, created by scattering x-rays off of graphene, have shown that the interaction among its electrons is surprisingly weak.
Graphene is a single atomic layer of carbon whose unusual electronic structure makes it a candidate for a new generation of low-cost, flexible electronics. A major outstanding question is whether the electrons in graphene move independently, or if their motion is correlated by Coulomb repulsion.
Using advanced x-ray scattering techniques, physicists in Peter Abbamonte’s group at the University of Illinois at Urbana-Champaign have imaged the motion of electrons in graphene with resolutions of 0.533 Å and 10.3 attoseconds. Their results were published on November 5 in Science.
Exactly how small and how fast are these measurements? An angstrom is 1/10,000,000,000 of a meter, about the width of a hydrogen atom. And an attosecond is to a second as a second is to the age of the universe.
The researchers found that graphene screens Coulomb interactions surprisingly effectively, causing it to act like a simple, independent-electron semimetal. Their work explains several mysteries, including why freestanding graphene fails to become an insulator as predicted. The study also demonstrates a new approach to studying ultrafast dynamics, creating a new window on the most fundamental properties of materials.
This work was supported by the U.S. Department of Energy under grants DE-FG02-07ER46459 and DE-FG02-07ER46453 through the Frederick Seitz Materials Research Laboratory, with use of the Advanced Photon Source supported by DEAC02-06CH11357. The conclusions presented are those of the researchers and do not necessarily reflect the views of the U.S. Department of Energy.