The quantization of conductance in the presence of non-magnetic point defects
is a consequence of topological protection and the spin-momentum locking of
helical edge states in two-dimensional topological insulators. This protection
ensures the absence of backscattering of helical edge modes in the quantum Hall
phase of the system. However, our study focuses on exploring a novel approach
to disrupt this protection. We propose that a linear arrangement of on-site
impurities can effectively lift the topological protection of edge states in
the Kane-Mele model. To investigate this phenomenon, we consider an armchair
ribbon containing a line defect spanning its width. Utilizing the tight-binding
model and non-equilibrium Green's function method, we calculate the
transmission coefficient of the system. Our results reveal a suppression of
conductance at energies near the lower edge of the bulk gap for positive
on-site potentials. To further comprehend this behavior, we perform analytical
calculations and discuss the formation of an impurity channel. This channel
arises due to the overlap of in-gap bound states, linking the bottom edge of
the ribbon to its top edge, consequently facilitating backscattering. Our
explanation is supported by the analysis of the local density of states at
sites near the position of impurities