Bose-Einstein condensates in quasi-periodic lattices: bosonic Josephson junction, self-trapping, and multi-mode dynamics

TL;DR

This paper investigates the dynamics of Bose-Einstein condensates in quasi-periodic lattices, demonstrating how localized states can simulate various physical regimes like Josephson junctions and self-trapping, with results supported by numerical simulations.

Contribution

It introduces a novel approach to emulate multi-well dynamics using localized states in quasi-periodic lattices, expanding understanding of nonlinear phenomena in BECs.

Findings

Localized states are homogeneously distributed below the mobility edge.

Superpositions of localized states can simulate Josephson and multi-mode dynamics.

Localized states and dynamics persist over long times in repulsive condensates.

Abstract

Bose-Einstein condensates loaded in one-dimensional bichromatic optical lattices with constituent sublattices having incommensurate periods is considered. Using the rational approximations for the incommensurate periods, we show that below the mobility edge the localized states are distributed nearly homogeneously in the space and explore the versatility of such potentials. We show that superposition of symmetric and anti-symmetric localized can be used to simulate various physical dynamical regimes, known to occur in double-well and multi-well traps. As examples, we obtain an alternative realization of a bosonic Josephson junction, whose coherent oscillations display beatings or switching in the weakly nonlinear regime, describe selftrapping and four-mode dynamics, mimicking coherent oscillations and self-trapping in four-well potentials. These phenomena can be observed for different pairs of modes, which are localized due to the interference rather than due to a confining trap. The results obtained using few-mode approximations are compared with the direct numerical simulations of the one-dimensional Gross-Pitaevskii equation. The localized states and the related dynamics are found to persist for long times even in the repulsive condensates. We also described bifurcations of the families of nonlinear modes, the symmetry breaking and stable minigap solitons.