Discrete solitons of spin-orbit coupled Bose-Einstein condensates in optical lattices

TL;DR

This paper investigates localized nonlinear excitations, including discrete solitons and breathers, in a spin-orbit coupled Bose-Einstein condensate within an optical lattice, revealing new asymmetric modes induced by SOC.

Contribution

It derives a tight-binding model incorporating spin-orbit coupling and demonstrates the existence, stability, and symmetry control of discrete solitons and breathers in this system.

Findings

Existence of stable discrete solitons and breathers with various symmetries.

Ability to switch mode symmetry from on-site to inter-site and asymmetric.

Identification of asymmetric modes as a novel feature of spin-orbit coupling.

Abstract

We study localized nonlinear excitations of a dilute Bose-Einstein condensate (BEC) with spin-orbit coupling in a deep optical lattice (OL). We use Wannier functions to derive a tight-binding model that includes the spin-orbit coupling (SOC) at the discrete level in the form of a generalized discrete nonlinear Sch\"odinger equation. Spectral properties are investigated and the existence and stability of discrete solitons and breathers with different symmetry properties with respect to the OL is demonstrated. We show that the symmetry of the modes can be changed from on-site to inter-site and to asymmetric modes simply by changing the interspecies interaction. Asymmetric modes appear to be novel modes intrinsic of the SOC.