Hall-potential investigations under quantum Hall conditions using scanning force microscopy

Hall-potential profiles of a two-dimensional electron system (2DES) under quantum Hall (QH) conditions have been investigated at T=1.4 K with submicron resolution using a scanning force microscope sensitive to electrostatics. At an even integer Landau level filling factor a rather nonlinear Hall-potential profile across the Hall-bar is observed. But at reduced magnetic field values corresponding to filling factors slightly above this even integer value almost no Hall-potential drop across the bulk region is found. Instead, the potential clearly drops across prominent areas associated with the positions of incompressible strips that just had emerged at that filling factor at both edges. This shows that the dominant incompressible strips of locally even integer filling factor can decouple the bulk from the edge, thus demonstrating the importance of the edge region for the Hall-field distribution even at non-integer filling factors.