Self-trapping of a binary Bose-Einstein condensate induced by interspecies interaction

TL;DR

This paper investigates the phenomenon of self-trapping in binary Bose-Einstein condensates within optical lattices and double wells, revealing conditions for permanent self-trapping driven by interspecies interactions and nonlinearities.

Contribution

It demonstrates how interspecies interactions can induce permanent self-trapping in binary BECs outside the natural nonlinearity window, expanding understanding of self-trapping mechanisms.

Findings

Self-trapping occurs within specific nonlinear windows in OL and DW.

In OL, self-trapping corresponds to stable gap solitons with breathing oscillations.

In DW, self-trapping is a dynamically stabilized state without a stationary counterpart.

Abstract

The problem of self-trapping of a Bose-Einstein condensate (BEC) and a binary BEC in an optical lattice (OL) and double well (DW) is studied using the mean-field Gross-Pitaevskii equation. For both DW and OL, permanent self-trapping occurs in a window of the repulsive nonlinearity $g$ of the GP equation: $g_{c1}<g<g_{c2}$. In case of OL, the critical nonlinearities $g_{c1}$ and $g_{c2}$ correspond to a window of chemical potentials $\mu_{c1}<\mu<\mu_{c2}$ defining the band gap(s) of the periodic OL. The permanent self-trapped BEC in an OL usually represents a breathing oscillation of a stable stationary gap soliton. The permanent self-trapped BEC in a DW, on the other hand, is a dynamically stabilized state without any stationary counterpart. For a binary BEC with intraspecies nonlinearities outside this window of nonlinearity, a permanent self trapping can be induced by tuning the interspecies interaction such that the effective nonlinearities of the components fall in the above window.