Transformation of a hybridized almost-zero mode into an absolute zero mode

For a finite-sized topologically non-trivial Su-Schrieffer-Heeger (SSH) model with an even number of sites, the existence of two almost-zero energy states which are exponentially localized on the left and right edge has been previously demonstrated. However, due to the hybridization of the modes, these states are not essentially robust against disorder; specifically in experimental setups where the system size is limited. We demonstrate that by introducing coupling defects to the initial structure, one of these topological modes is repelled from zero, whereas the other turns into an absolute zero mode localized on one of the edges of the lattice which can be robust against certain disorders in the structure.