Photon-atomic solitons in a Bose-Einstein condensate trapped in a soft optical lattice

TL;DR

This paper demonstrates the formation of stable photon-atomic lattice solitons in a Bose-Einstein condensate within a soft optical lattice, driven by local-field effects, without atomic interactions, revealing new self-trapped ground states.

Contribution

It introduces a novel mechanism for creating stable photon-atomic solitons in a BEC using local-field effects, independent of atomic collisional interactions.

Findings

Stable photon-atomic lattice solitons are generated in a BEC without atomic interactions.

The solitons include an optical component deforming the optical lattice.

A transition from loosely bound to tightly bound modes occurs with increasing atom number.

Abstract

We investigate the ground state (GS) of a collisionless Bose-Einstein condensate (BEC) trapped in a soft one-dimensional optical lattice (OL), which is formed by two counterpropagating optical beams perturbed by the BEC density profile through the local-field effect (LFE). We show that LFE gives rise to an envelope-deformation potential, a nonlocal potential resulting from the phase deformation, and an effective self-interaction of the condensate. As a result, stable photon-atomic lattice solitons, including an optical component, in the form of the deformation of the soft OL, in a combination with a localized matter-wave component, are generated in the blue-detuned setting, without any direct interaction between atoms. These self-trapped modes, which realize the system's GS, are essentially different from the gap solitons supported by the interplay of the OL potential and collisional interactions between atoms. A transition to tightly bound modes from loosely bound ones occurs with the increase of the number of atoms in the BEC.