Investigation of a non-Hermitian edge burst with time-dependent perturbation theory

Edge burst is a phenomenon in non-Hermitian quantum dynamics discovered by a recent numerical study [Phys. Rev. Lett. 128, 120401 (2022)]. It finds that a large proportion of particle loss occurs at the system boundary in a class of non-Hermitian quantum walk. In this paper, we investigate the evolution of real-space wave functions for this lattice system. We find the wave function of the edge site is distinct from the bulk sites. Using time-dependent perturbation theory, we derive the analytical expression of the real-space wave functions and find that the different evolution behaviors between the edge and bulk sites are due to their different nearest-neighbor site configurations. We also find the edge wave function primarily results from the transition of the two nearest-neighbor nondecay sites. Besides, the numerical diagonalization shows the edge wave function is mainly propagated by a group of eigenmodes with a relatively large imaginary part. Our work provides an analytical method for studying non-Hermitian quantum dynamical problems.