Robustness of helical edge states under edge reconstruction

¹ Institut für Theoretische Physik, Universität Leipzig - D-04103, Leipzig, Germany
² Department of Physics and Astronomy, University of Tennessee - Knoxville, TN 37996, USA
³ Min H. Kao Department of Electrical Engineering and Computer Science, University of Tennessee Knoxville, TN 37996, USA
⁴ Institute for Advanced Materials and Manufacturing, University of Tennessee - Knoxville, TN 37996, USA

^(a) E-mail: rosenow@physik.uni-leipzig.de (corresponding author)

Received: 14 June 2022
Accepted: 27 September 2022

Abstract

The helical edge states of time-reversal invariant two-dimensional topological insulators are protected against backscattering in idealized models. In more realistic scenarios with a shallow confining potential at the sample boundary, additional strongly interacting edge states may arise, that could interfere with the topological protection of edge conduction. We find that interaction effects within the reconstructed edges are well described by the Luttinger liquid model. While interactions between this Luttinger liquid and the helical edge states can in principle give rise to dynamical spin polarization and the breaking of time-reversal symmetry, we demonstrate that random spin-orbit coupling strongly suppresses such dynamical spin polarization, resulting in the persistence of near quantized edge conduction.