Résumé:

Recently, a type of topological invariance was predicted in materials with band inversion (semiconductor with a gap between the upper p-type and lower s-type energy bands) due to strong spin-orbit coupling . In this case, one speaks of topological insulators.2 This kind of topologically protected surface state was first demonstrated to exist in two-dimensional HgTe/CdTe quantum wells (QWs).3,4 In this work, we report on a Terahertz magneto-photoconductivity study of inverted band structure HgTe-based Field Effect Transistor (FET) : i) We observe a resonance that could be attributed to topological phase transition related to anticrossing of the zero-mode Landau levels at a critical value of the magnetic field5. ii) We also observe unknown resonances in the direct band structure regime which are shifting to higher magnetic field values with increasing gate voltage. These resonances cannot be attributed to magnetoplasmons and may be linked with impurity resonant transitions. iii) We finally observe the cyclotron resonance line giving electron effective mass m* = 0.03 m0.