Seltrapping in flat band lattices with nonlinear disorder

TL;DR

This paper investigates how nonlinear disorder affects selftrapping of localized excitations in flat band lattices, revealing regimes of degeneracy-controlled linear trapping and environment-dependent nonlinear trapping, with wavefunction spreading often inhibited.

Contribution

It introduces a detailed analysis of selftrapping in flat band lattices with nonlinear disorder, including a solvable model explaining degeneracy effects.

Findings

In weak nonlinearity, selftrapping is governed by band degeneracy.

In strong nonlinearity, local environment influences trapping behavior.

Wavefunction spreading is halted in about 50% of cases with random nonlinearity.

Abstract

We study the selftrapping properties of an initially localized excitation in several flat band lattices, in the presence of nonlinear (Kerr) disorder. In the weak nonlinearity regime, the dynamics is controlled by the degeneracy of the bands leading to a linear form of selftrapping. In the strong nonlinearity regime, the dynamics of the excitations depends strongly on the local environment around the initial excitation site that leads to a highly fluctuating selfrapping profile. It is shown that the spreading of the wavefunction in the presence of random nonlinearity, is always completely inhibited about fifty percent of all cases. The role of degeneracy associated with the flatbands is explained with the help of the $n$-simplex system, which can be solved in closed form.