Solitons in tunnel-coupled repulsive and attractive condensates

TL;DR

This paper investigates the existence and stability of unusual bright solitons in a double-well Bose-Einstein condensate with opposite signs of scattering length, highlighting the role of quantum tunneling and coupling strength.

Contribution

It introduces a novel analysis of stable bright solitons in coupled condensates with mixed interactions, emphasizing the impact of tunneling and coupling regimes.

Findings

Unusual stable bright solitons with atoms in the repulsive part.

Stability derived from quantum tunneling and strong coupling.

Ground state favors weak coupling with atoms in the attractive part.

Abstract

We study solitons in the condensate trapped in a double-well potential with far-separated wells, when the s-wave scattering length has different signs in the two parts of the condensate. By employing the coupled-mode approximation it is shown that there are unusual stable bright solitons in the condensate, with the larger share of atoms being gathered in the repulsive part. Such unusual solitons derive their stability from the quantum tunneling and correspond to the strong coupling between the parts of the condensate. The ground state of the system, however, corresponds to weak coupling between the condensate parts, with the larger share of atoms being gathered in the attractive part of the condensate.