Topologically Quantized Soliton-Like Pumping using Synthetic Nonlinearity

TL;DR

This paper demonstrates that synthetic nonlinearity in topological lattice models enables quantized soliton pumping, revealing new fractional quantization phenomena and restoring consistency with linear Thouless pumping.

Contribution

It introduces a synthetic nonlinearity in the AAH model that enables soliton-like quantized pumping and fractional quantization, connecting nonlinear excitations with topological invariants.

Findings

Quantized soliton pumping observed with localized excitations.

Synthetic nonlinearity restores Wannier function correspondence.

Fractional quantization arises in multi-band systems.

Abstract

The interplay between nonlinear and topological physics has led to intriguing emergent phenomena, such as quantized and fractionally quantized Thouless pumping of solitons dictated by the topological invariants of the underlying band structure. Unlike linear Thouless pumping, which requires excitation of a Wannier function of a uniformly filled band, quantized soliton pumping is observed even with localized excitations that do not represent Wannier functions. Here, we show that similar soliton-like quantized pumping can be observed in Aubry-Andre-Harper (AAH) model by introducing a synthetic nonlinearity in the form of a cutoff on the coupling strengths between lattice sites. More importantly, we reveal that the localized excitations driving quantized soliton pumping are precisely the Wannier functions of the uniformly filled bands of the effectively nonlinear lattice, thus restoring consistency with linear Thouless pumping. We extend this approach to multi-band systems and show that the nonlinearity introduces a degeneracy between bands, subsequently leading to the observation of fractionally quantized pumping. Our approach of introducing a synthetic nonlinearity is general and could be extended to reveal soliton dynamics in other nonlinear topological systems.