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Transition between ordinary and topological insulator regimes in two-dimensional resonant magnetotransport

In the two-dimensional case the transition between ordinary and topological insulator states can be described by a massive Dirac model with the mass term changing its sign at the transition point. We theoretically investigate how such a transition manifests itself in resonant transport via localized helical edge states. The resonance occurs in the middle of the band gap due to a zero edge-state mode which is protected by the time-reversal symmetry, also when coupled to the conducting leads. We obtain the explicit dependence of the resonant conductance on the mass parameter and an external magnetic field. The proposal may be of practical use, allowing one to determine the orbital g-factor of helical edge states in two-dimensional topological insulators.