Spatially resolving density-dependent screening around a single charged atom in graphene

Author(s): Wong, D; Corsetti, F; Wang, Y; Brar, VW; Tsai, HZ; Wu, Q; Kawakami, RK; Zettl, A; Mostofi, AA; Lischner, J; Crommie, MF | Abstract: © 2017 American Physical Society. Electrons in two-dimensional graphene sheets behave as interacting chiral Dirac fermions and have unique screening properties due to their symmetry and reduced dimensionality. By using a combination of scanning tunneling spectroscopy measurements and theoretical modeling we have characterized how graphene's massless charge carriers screen individual charged calcium atoms. A backgated graphene device configuration has allowed us to directly visualize how the screening length for this system can be tuned with carrier density. Our results provide insight into electron-impurity and electron-electron interactions in a relativistic setting with important consequences for other graphene-based electronic devices.