Self-trapping and skin solitons in two-dimensional non-Hermitian lattices

TL;DR

This paper explores how nonlinearity affects wave localization and skin solitons in two-dimensional non-Hermitian lattices, revealing position-dependent thresholds and new soliton solutions.

Contribution

It demonstrates the interplay between nonlinearity and non-Hermitian effects, identifying skin solitons and analyzing boundary localization in 2D lattices with asymmetric couplings.

Findings

Self-trapping occurs above a critical amplitude near localized eigenmodes.

Lower thresholds for confinement near the lattice edges.

Identification of skin soliton solutions in various geometries.

Abstract

Two-dimensional non-Hermitian photonic lattices with asymmetric couplings offer rich possibilities for controlling wave localization, through the emergence of the non-Hermitian skin effect at lattice corners or sides. Incorporating optical nonlinearity fundamentally alters these boundary-localization characteristics. Here we show that in a two-dimensional Hatano-Nelson lattice with Kerr nonlinearity, the interplay between self-trapping and directional propagation leads to position dependent amplitude thresholds. Single-site excitations having above a critical amplitude become confined to their initial position, with lower thresholds near the position where the linear eigenmodes are localized and higher thresholds within the lattice's bulk. Additionally, we study the differences of this dynamical interplay, for wider initial excitations, between the focusing and defocusing Kerr-nonlinearity regimes. Lastly, we identify skin soliton solutions in a variety of two-dimensional lattice geometries featuring coupling asymmetry.