Electro-optic imaging of potential distributions in the quantum Hall regime

The potential distribution in Hall effect experiments on two-dimensional electron systems (2DES) is imaged with a scanning polarization optical microscope utilizing the internal electro-optic effect. Outside the quantum Hall regime (QHR), Hall potential profiles vary linearly between the two edges. In the QHR, the observed Hall potential profile is nonlinear. Its shape depends on magnetic field and current, indicating inhomogeneous current transport in the interior of the 2DES. In the plateau centre, the Hall potential drop is concentrated in the middle of the channel. The results are interpreted in terms of electron density inhomogeneities. These lead to the observed potential distributions because of the very strong dependence of the conductivity on the local electron density.