  The robustness of topological materials against disorder and defects is
presumed but has not been demonstrated explicitly in realistic systems. In this
work, we use state-of-the-art density functional theory and recursive
nonequilibrium Green's functions methods to study the effect of disorder in the
electronic transport of long nanoribbons, up to 157 nm, as a function of
vacancy concentration. In narrow nanoribbons, even for small vacancy
concentrations, defect-like localized states give rise to hybridization between
the edge states erasing topological protection and enabling backscattering
events. We show that the topological protection is more robust for wide
nanoribbons, but surprisingly it breaks down at moderate structural disorder.
Our study helps to establish some bounds on defective bismuthene nanoribbons as
promising candidates for spintronic applications.
