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arXiv · 1004.0194

Interaction-enhanced magnetically ordered insulating state at the edge of a two-dimensional topological insulator

Maxim Kharitonov
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Abstract

We develop a theory of the correlated magnetically ordered insulating state at the edge of a two-dimensional topological insulator. We demonstrate that the gapped spin-polarized state, induced by the application of the magnetic field $B$, is naturally facilitated by electron interactions, which drive the critical easy-plane ferromagnetic correlations in the helical liquid. As the key manifestation, the gap $\De$ in the spectrum of collective excitations, which carry both spin and charge, is enhanced and exhibits a scaling dependence $\De \propto B^{1/(2-K)}$, controlled by the Luttinger liquid parameter $K$. This scaling dependence could be probed through the activation behavior $G \sim (e^2/h) \exp(- \De/T)$ of the longitudinal conductance of a Hall-bar device at lower temperatures, providing a straightforward way to extract the parameter $K$ experimentally. Our findings thus suggest that the signatures of the interaction-driven quantum criticality of the helical liquid could be revealed already in a standard Hall-bar measurement.

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Maxim Kharitonov. 2010-04-01. Interaction-enhanced magnetically ordered insulating state at the edge of a two-dimensional topological insulator. https://doi.org/10.1103/physrevb.86.165121

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