Non-Hermitian systems have provided a rich platform to study unconventional topological phases. These phases are usually robust against external perturbations that respect certain symmetries of the system. In this Letter, we provide a different method to analytically study the effect of disorder, using tools from quantum field theory applied to discrete models around the phase-transition points. We investigate two different onedimensional models, the paradigmatic non-Hermitian Su-Schrieffer-Heeger model and an s-wave superconductor with imbalanced pairing. These analytic results are compared to numerical simulations in the discrete models. It is found that the systems are driven from a topological to a trivial phase in the same way.

We study the properties of the one-dimensional Fibonacci chain, subjected to the placement of on-site impurities. The resulting disruption of quasiperiodicity can be classified in terms of the renormalization path of the site at which the impurity is placed, which greatly reduces the possible amount of disordered behavior that impurities can induce. Moreover, it is found that, to some extent, the addition of multiple weak impurities can be treated by superposing the individual contributions together and ignoring nonlinear effects. This means that a transition regime between quasiperiodic order and disorder exists in which some parts of the system still exhibit quasiperiodicit, while other parts start to be characterized by different localization behaviors of the wave functions. This is manifested through a symmetry in the wave-function amplitude map, expressed in terms of conumbers, and through the inverse participation ratio. For the latter, we find that its average of states can also be grouped in terms of the renormalization path of the site at which the impurity has been placed.