Weak antilocalization in HgTe double wells with massive Dirac fermions

The HgTe double quantum well is a two-dimensional topological insulator in which the bulk carriers are massive Dirac fermions with a vanishingly small Berry curvature. Accordingly, the nature of quantum corrections to the conductivity in such a system should be determined by the presence of two factors: a near-zero Berry phase and spin-orbit scattering. In particular, the vanishing Berry curvature in the HgTe double quantum well should, according to the theory, lead to the observation of negative magnetoresistance, while in a single HgTe quantum well with massless Dirac fermions and a non-zero Berry phase, the theory always predicts antilocalization corrections to the conductivity (positive magnetoresistance) regardless of the strength of the spin-orbit interaction. In the present work, contrary to expectations, similar antilocalization corrections to the conductivity of positive magnetoresistance were also found in the double HgTe quantum well, which indicates the dominance of the spin-orbit relaxation mechanism in quantum transport, leading to weak antilocalization. Thus, the results of our study of interference corrections to the conductivity in the system of massive Dirac fermions indicate that the physics of localization in two-dimensional topological insulators is determined by the competition of such factors as the spin texture, the mass of the quasiparticle, and the intensity of spin-orbit scattering.