Conductance suppression by nonmagnetic point defects in helical edge channels of two-dimensional topological insulators

Abstract

We study backscattering of electrons and conductance suppression in a helical edge channel in two-dimensional topological insulators with broken axial spin symmetry in the presence of nonmagnetic point defects that create bound states. In this system the tunneling coupling of the edge and bound states results in the formation of composite helical edge states in which all four partners of both Kramers pairs of the conventional helical edge states and bound states are mixed. The backscattering is considered as a result of inelastic two-particle scattering of electrons, which are in these composite states. Within this approach we find that sufficiently strong backscattering occurs even if the defect creates only one energy level. The effect is caused by electron transitions between the composite states with energy near the bound state level. We study the deviation from the quantized conductance due to scattering by a single defect as a function of temperature and Fermi level. The results are generalized to the case of scattering by many different defects with energy levels distributed over the band gap. In this case, the conductance deviation turns out to be quite strong and comparable with experiment even at a sufficiently low density of defects. Interestingly, under certain conditions, the temperature dependence of the conductance deviation becomes very weak over a wide temperature range.

15 pages, 8 figures

References in corpus (15)

• Quantum Spin Hall Effect and Topological Phase Transition in HgTe Quantum Wells
• Quantum Spin Hall Insulator State in HgTe Quantum Wells
• The Quantum Spin Hall Effect: Theory and Experiment
• The Helical Liquid and the Edge of Quantum Spin Hall Systems
• Kondo effect in the helical edge liquid of the quantum spin Hall state
• Conductance of a helical edge liquid coupled to a magnetic impurity
• Resistance of helical edges formed in a semiconductor heterostructure
• Conductivity of a generic helical liquid
• Spatially resolved study of backscattering in the quantum spin Hall state
• Renormalization group approach for the scattering off a single Rashba impurity in a helical liquid
• Spontaneous breakdown of topological protection in two dimensions
• Mesoscopic transport in two-dimensional topological insulators
• Electronic states induced by nonmagnetic defects in two-dimensional topological insulators
• Non-magnetic defects in the bulk of two-dimensional topological insulators
• Optical transitions in two-dimensional topological insulators with point defects

Cited by in corpus (2)

• Nonlinear optical absorption and photocurrents in topological insulators
• Formation of bound states from the edge states of 2D topological insulator by macroscopic magnetic barriers