Nonadiabatic nonlinear non-Hermitian quantized pumping

Abstract

We analyze a quantized pumping in a nonlinear non-Hermitian photonic system with nonadiabatic driving. The photonic system is made of a waveguide array, where the distances between adjacent waveguides are modulated. It is described by the Su-Schrieffer-Heeger model together with a saturated nonlinear gain term and a linear loss term. A topological interface state between the topological and the trivial phases is stabilized by the combination of a saturated nonlinear gain term and a linear loss term. We study the pumping of the topological interface state. We define the transfer-speed ratio $\omega /\mathrm{\Omega }$ by the ratio of the pumping speed $\omega$ of the center of mass of the wave packet to the driving speed $\mathrm{\Omega }$ of the topological interface. It is quantized topologically as $\omega /\mathrm{\Omega }=1$ in the adiabatic limit. It remains to be quantized dynamically unless the driving is not too fast even in the nonadiabatic regime. On the other hand, the wave packet collapses and there is no quantized pumping when the driving is too fast. In addition, the stability against disorder is more enhanced by stronger nonlinearity.