Experimental evidence for edge-like states in three-dimensional electron systems - art. no. 205104

The local density of states (DOS) of n-InAs(110) is measured in the extreme quantum limit by low-temperature scanning tunneling microscopy. Based on t he general trends published previously [Phys. Rev. Lett. 86. 1582 (2001)] w e analyze the data in more detail. First the influence of the tip induced q uantum dot is studied. It turns out that the observed serpentine structures are not correlated with the properties of the quantum dot, which lead us t o the conclusion that they are caused by the three-dimensional (3D) DOS of the semiconductor. The serpentine structures move with increasing energy si milar to equipotential lines of a two-dimensional potential landscape. With increasing magnetic field additional serpentines appear until a complete n etwork penetrates the visible area. Moreover, an uncorrugated DOS coexists with the serpentine structures up to the highest magnetic field of 6 T. The results lead us to the conclusion that an increasing part of the DOS is lo calized in the direction parallel to the magnetic field, effectively acting as a two-dimensional DOS and thus exhibiting edgelike states. This implies that the steplike feature of the Hall resistance in the extreme quantum li mit is a precursor of a quantized Hall step.