| Nov 10, 2010 |
Ultrafast imaging of electron waves in graphene
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(Nanowerk News) 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.
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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.
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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 ("The Effective Fine-Structure Constant of Freestanding Graphene Measured in Graphite").
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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.
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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.
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The experiments were carried out at the Frederick Seitz Materials Research Laboratory at the University of Illinois and the Advanced Photon Source at Argonne National Laboratory.
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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.
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