Modulational instability in Bose--Einstein condensate in optical superlattice

TL;DR

This paper investigates the modulational instability of Bose-Einstein condensates in optical superlattices, revealing conditions for instability, analyzing growth rates, and demonstrating the evolution into solitary peaks through numerical simulations.

Contribution

It provides a linear stability analysis and numerical simulations of modulational instability in BECs within optical superlattices, highlighting the instability at high densities.

Findings

Steady state distributions become unstable at high boson densities.

The growth rate of modulational instability was derived.

Numerical simulations show evolution into solitary peaks before chaos.

Abstract

We consider the Bose-Einstein condensate trapped in optical lattice, which is formed from two kinds of deep potentials. The tight-binding approximation was used. Steady state distribution of the probability amplitudes and the site population in the one dimensional optical superlattice were found. It was shown that this solution of the equations which describe the dynamics of the Bose-Einstein condensate in superlattice is unstable at the sufficiently high density of the bosons. The expression for increment of the modulational instability was found on base of the linear stability analysis. Numerical simulation demonstrates the evolution of the steady state distributions of bosons into the space array of the solitary peaks before the chaotic regime generation.