Magnetic moments in a helical edge can make weak correlations seem strong

Abstract

We study the effect of localized magnetic moments on the conductance of a helical edge. Interaction with a local moment is an effective backscattering mechanism for the edge electrons. We evaluate the resulting differential conductance as a function of temperature $T$ and applied bias $V$ for any value of $V/T$. Backscattering off magnetic moments, combined with the weak repulsion between the edge electrons results in a power-law temperature and voltage dependence of the conductance; the corresponding small positive exponent is indicative of insulating behavior. Local moments may naturally appear due to charge disorder in a narrow-gap semiconductor. Our results provide an alternative interpretation of the recent experiment by Li et al. \cite{Li15} where a power-law suppression of the conductance was attributed to strong electron repulsion within the edge, with the value of Luttinger liquid parameter $K$ fine-tuned close to $1/4$.

Updated to match published version, now 6+8 pages

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• Interplay between Rashba interaction and electromagnetic field in the edge states of a 2D topological insulator
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• Multi-probe analysis to separate edge currents from bulk currents in quantum spin Hall insulators and to analyze their temperature dependence
• Transport in Magnetically Doped One-Dimensional Wires: Can the Helical Protection Emerge without the Global Helicity?
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• Interaction- and phonon-induced topological phase transitions in double helical liquids
• Finite-temperature spectroscopy of dirty helical Luttinger liquids
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• Protected helical transport in magnetically doped quantum wires: Beyond the one-dimensional paradigm
• Role of magnetic doping in topological HgTe and application of the Gram-Schmidt method for computing impurity states in quantum wells