  Learning the electron scattering around atomic impurities is a fundamental
step to fully understand the basic electronic transport properties of realistic
conducting materials. Although many efforts have been made in this field for
several decades, atomic scale transport around single point-like impurities has
yet been achieved. Here, we report the direct visualization of the electric
current induced dipoles around single atomic impurities in epitaxial bilayer
graphene by multi-probe low temperature scanning tunneling potentiometry as the
local current density is raised up to around 25 A/m, which is considerably
higher than that in previous studies. We find the directions of these dipoles
which are parallel or anti-parallel to local current are determined by the
charge polarity of the impurities, revealing the direct evidence for the
existence of the carrier density modulation effect proposed by Landauer in
1976. Furthermore, by $in$ $situ$ tuning local current direction with contact
probes, these dipoles are redirected correspondingly. Our work paves the way to
explore the electronic quantum transport phenomena at single atomic impurity
level and the potential future electronics toward or beyond the end of Moore's
Law.
