Quantum hall effect in n-p-n and n-2D topological insulator-n junctions.

We have studied quantized transport in HgTe wells with inverted band structure corresponding to the two-dimensional topological insulator phase (2D TI) with locally controlled density allowing n-p-n and n-2D TI-n junctions. The resistance reveals the fractional plateau 2h/e(2) in the n-p-n regime in the presence of the strong perpendicular magnetic field. We found that in the n-2D TI-n regime the plateaux in resistance in not universal and results from the edge state equilibration at the interface between chiral and helical edge modes. We provided the simple model describing the resistance quantization in n-2D TI-n regime.