Mapping Dirac quasiparticles near a single Coulomb impurity on graphene
Author(s)Wang, Yang; Brar, Victor W.; Shytov, Andrey V.; Wu, Qiong; Regan, William; Tsai, Hsin-Zon; Zettl, Alex; Crommie, Michael F.; Levitov, Leonid; ... Show more Show less
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The response of Dirac fermions to a Coulomb potential is predicted to differ significantly from how non-relativistic electrons behave in traditional atomic and impurity systems. Surprisingly, many key theoretical predictions for this ultra-relativistic regime have not been tested. Graphene, a two-dimensional material in which electrons behave like massless Dirac fermions, provides a unique opportunity to test such predictions. Graphene’s response to a Coulomb potential also offers insight into important material characteristics, including graphene’s intrinsic dielectric constant, which is the primary factor determining the strength of electron–electron interactions in graphene. Here we present a direct measurement of the nanoscale response of Dirac fermions to a single Coulomb potential placed on a gated graphene device. Scanning tunnelling microscopy was used to fabricate tunable charge impurities on graphene, and to image electronic screening around them for a Q = +1|e| charge state. Electron-like and hole-like Dirac fermions were observed to respond differently to a Coulomb potential. Comparing the observed electron–hole asymmetry to theoretical simulations has allowed us to test predictions for how Dirac fermions behave near a Coulomb potential, as well as extract graphene’s intrinsic dielectric constant: ε[subscript g] = 3.0±1.0. This small value of ε[subscript g] indicates that electron–electron interactions can contribute significantly to graphene properties.
DepartmentMassachusetts Institute of Technology. Department of Physics
Nature Publishing Group
Wang, Yang, Victor W. Brar, Andrey V. Shytov, Qiong Wu, William Regan, Hsin-Zon Tsai, Alex Zettl, Leonid S. Levitov, and Michael F. Crommie. “Mapping Dirac Quasiparticles Near a Single Coulomb Impurity on Graphene.” Nature Physics 8, no. 9 (July 29, 2012): 653–657.