  In this paper, we address the question of stability of protected chiral modes
(e.g., helical edge states at the boundary of two-dimensional topological
insulators) upon interactions with the external bath. Namely, we study how
backscattering amplitude changes when different interaction channels between
the system and the environment are present. Depending on the relative strength
of the Coulomb and spin-spin channels, we discover three different possible
regimes. While the Coulomb interaction on its own naturally amplifies the
backscattering and destroys the protection of chiral modes, and the spin-spin
channel marginally suppresses backscattering, their interplay can make the
backscattering process strictly irrelevant, opening the possibility to use the
external spin bath as a stabilizer that alleviates destructive effects and
restores the chirality protection.

Mesoscale and Nanoscale Physics;Strongly Correlated Electrons