Seminarium Fizyki Materii Skondensowanej

First part of my talk will contain an introduction to the subject of socalled topological insulators. I will then present an effective mediumtheory that explains the disorder-induced transition into a phase ofquantized conductance, discovered in computer simulations of CdHgTequantum wells. The calculated location of the phase boundary at weakdisorder agrees with numerical simulations pointing to the underlyingcrossing of a band edge rather than a mobility edge. The strong disorderphase boundary can be interpreted as an insulator-insulator transition inthe universality class of integer quantum Hall effect.