Interaction-enhanced magnetically ordered insulating state at the edge of a two-dimensional topological insulator
Year: 2012
Type: article
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 $\mathbit{\ensuremath{\Delta}}$ in the spectrum of collective excitations, which carry both spin and charge, is enhanced and exhibits a scaling dependence $\mathbit{\ensuremath{\Delta}}\ensuremath{\propto}{B}^{1/(2\ensuremath{-}K)}$, controlled by the Luttinger liquid parameter $K$. This scaling dependence could be probed through the activation behavior $G\ensuremath{\sim}({e}^{2}/h)\mathrm{exp}(\ensuremath{-}\mathbit{\ensuremath{\Delta}}/T)$ 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.
Source: Physical Review B
Author: Maxim Kharitonov
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funder: U.S. Department of Energy
OpenAlex ID: W2168370995