  The integer quantized Hall effect reveals a state of scattering-free carrier
transport and quantized resistance in a two-dimensional conductor exposed to a
perpendicular magnetic field. The quantized resistance is observed for the Hall
bar geometry, i.e., if the current carrying contacts are connected by sample
edges. A widely accepted model is the Landauer-Buttiker picture, which assumes
an incompressible, i.e., electrically insulating bulk state surrounded by
one-dimensional edge channels giving rise to quantized resistance. This model
is challenged by the screening theory, which takes into account
electron-electron interaction and predicts for the quantized Hall plateaus
current flow in incompressible strips, which gradually shifts from the sample
edges into the bulk with increasing magnetic field. We present direct proof of
the predicted scattering-free bulk transport by exploring a Hall bar augmented
with an additional contact placed in its center away from the Hall bar edges.
Our result supports the screening theory.
