Quantum hall effect in a system of gapless Dirac fermions in HgTe quantum wells

Abstract

The specific features of the quantum Hall effect (QHE) in a system of gapless Dirac fermions in HgTe quantum wells have been studied. It has been established that the behavior of the QHE is asymmetric with respect to the Dirac point: at the lowest temperature (0.2 K), quantization of hole fermions occurs in weak magnetic fields down to 0.15 T, whereas quantization of the electron part of the Dirac cone occurs only in fields of about 0.5 T. Such an asymmetry is caused by the effect of sideband maxima in the valence band forming the heavy-hole valleys, which play the role of a reservoir and screen out the fluctuation potential. The analysis of the behavior of the dissipative component of the conductivity near the Dirac point has led to a conclusion on the existence of the zeroth Landau level at this point.