Non-Hermitian excitations in nonlinear topological lattice

Nonlinear effects and non-Hermitian phenomena unveil additional intricate facets in topological matter physics. They can naturally intertwine to enable advanced functionalities in topolectrical circuits and photonic structures. Here, we illustrate the subtle interplay between nonlinearity and non-Hermiticity by examining the characteristics of small wave perturbations on the background of the self-induced topological edge state in the nonlinear Su-Schrieffer-Heeger model. We demonstrate that their underlying physics is captured by the non-Hermitian effective Hamiltonian, which features nonreciprocal coupling terms and entails unconventional time-dependent field localization.