Transport of Dirac fermions in HgTe quantum wells: Mobility anomaly and weak antilocalization

Recent studies of the quantum Hall effect and the minimal conductivity in HgTe quantum wells have shown that this electronic system exhibits a single-valley Dirac fermion spectrum. In this work, we investigate further manifestations of the Dirac fermion transport in HgTe quantum wells: nonmonotonic carrier-density-dependent mobility and weak antilocalization effects. We demonstrate both theoretically and experimentally that the carrier mobility has a maximum due to the competition of two disorder scattering mechanisms, viz. scattering by charged impurities and by quantum-well-width fluctuations which induce a fluctuating band gap, or, equivalently, fluctuating Dirac mass. Using the cooperon description of quantum interference effects, we also analyze how the symmetry breaking due to the finite band gap (Dirac mass) influences the weak antilocalization correction to the Drude conductivity.