Résumé:

Surface states in semiconducting materials are usually fragile with respect to disorder and perturbations. However, there are systems in which surface states become robust because of the non-trivial topology of the band structure. A well-known example is the integer quantum Hall effect in which magnetic field splits conduction band of 2D carriers into discrete energy levels (Landau levels) inducing specific edge channels of quantized conductance. But recently, another type of topological phase was identified in materials with energy band inversion and strong spin orbit interaction. It is called the topological insulator phase. The most interesting property of 2D topological insulators is the presence of spin polarized counter-propagating edge channels of quantized conductance, protected from back scattering. The topologically nontrivial state was first realized in HgTe-based quantum wells.