Generic helical edge states due to Rashba spin-orbit coupling in a topological insulator

Abstract

We study the helical edge states of a two-dimensional topological insulator without axial spin symmetry due to the Rashba spin-orbit interaction. Lack of axial spin symmetry can lead to so-called generic helical edge states, which have energy-dependent spin orientation. This opens the possibility of inelastic backscattering and thereby nonquantized transport. Here we find analytically the new dispersion relations and the energy dependent spin orientation of the generic helical edge states in the presence of Rashba spin-orbit coupling within the Bernevig-Hughes-Zhang model, for both a single isolated edge and for a finite width ribbon. In the single-edge case, we analytically quantify the energy dependence of the spin orientation, which turns out to be weak for a realistic HgTe quantum well. Nevertheless, finite size effects combined with Rashba spin-orbit coupling result in two avoided crossings in the energy dispersions, where the spin orientation variation of the edge states is very significantly increased for realistic parameters. Finally, our analytical results are found to compare well to a numerical tight-binding regularization of the model.

21 pages (main text 11 pages), 11 figures

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Cited by in corpus (13)

• Interacting topological edge channels
• Helical Liquids in Semiconductors
• Spin-polarization control driven by a Rashba-type effect breaking the mirror symmetry in two-dimensional dual topological insulators
• Current-induced gap opening in interacting topological insulator surfaces
• Superconducting Quantum Interference in Edge State Josephson Junctions
• Elastic backscattering of quantum spin Hall edge modes from Coulomb interactions with non-magnetic impurities
• Explicit derivation of the chiral and (generic) helical edge states for the Kane-Mele model: Closed expressions for the wave function, dispersion relation, and spin rotation
• Spin field-effect transistor in a quantum spin-Hall device
• Dual topological insulator with mirror symmetry protected helical edge states
• Rashba coupling and spin switching through surface states of Dirac semimetals
• Long-range perturbation of helical edge states by nonmagnetic defects in two-dimensional topological insulators
• Transport signatures of a quantum spin Hall - chiral topological superconductor junction
• Manipulation of helical states revealed by crossed Andreev reflection