Interference-induced magnetoresistance in HgTe quantum wells

We study the quantum interference correction to the conductivity in HgTe quantum wells using the Bernevig-Hughes-Zhang model. This model consists of two independent species (blocks) of massive Dirac fermions. We describe the crossover between the orthogonal and symplectic classes with increasing the carrier concentration and calculate, respectively, weak localization and antilocalization corrections in the absence of the block mixing and assuming the white-noise disorder within each block. We have calculated the interference-induced magnetoresistance in a wide interval of magnetic fields, in particular, beyond the diffusion regime. Remarkably, each Dirac cone taken separately gives a linear contribution to the low-field magnetoresistance, which turns out to be asymmetric in magnetic field B. We present an interpretation of this result in terms of the Berry-phase formalism. The contributions of the two blocks are related to each other by replacing B to -B, so that the total magnetoresistance is symmetric and parabolic in the limit B -> 0. However, in some range of parameters, field dependence turns out to be strongly nonmonotonous. We also demonstrate that block mixing gives rise to additional singular diffusive modes which do not show up in the absence of mixing.