Effective spin dephasing mechanism in confined two-dimensional topological insulators

TL;DR

This paper uncovers an effective spin dephasing mechanism in 2D topological insulators, showing how Rashba spin-orbit coupling and electron-phonon interactions cause inelastic backscattering without breaking time-reversal symmetry.

Contribution

It introduces a novel spin dephasing mechanism in quantum spin Hall systems modeled as quantum dots, explaining backscattering phenomena while preserving time-reversal symmetry.

Findings

Spin dephasing arises from Rashba coupling and electron-phonon interactions.

Inelastic backscattering occurs in topological insulator quantum dots.

Results explain robust edge transport in InAs/GaSb QSH systems.

Abstract

A Kramers pair of helical edge states in quantum spin Hall effect (QSHE) is robust against normal dephasing but not robust to spin dephasing. In our work, we provide an effective spin dephasing mechanism in the puddles of two-dimensional (2D) QSHE, which is simulated as quantum dots modeled by 2D massive Dirac Hamiltonian. We demonstrate that the spin dephasing effect can originate from the combination of the Rashba spin-orbit coupling and electron-phonon interaction, which gives rise to inelastic backscattering in edge states within the topological insulator quantum dots, although the time-reversal symmetry is preserved throughout. Finally, we discuss the tunneling between extended helical edge states and local edge states in the QSH quantum dots, which leads to backscattering in the extended edge states. These results can explain the more robust edge transport in InAs/GaSb QSH systems.