Interfaces between Bose-Einstein and Tonks-Girardeau atomic gases

TL;DR

This paper explores the interfaces between Bose-Einstein condensates and Tonks-Girardeau gases in one dimension, analyzing domain walls, bubble drops, and soliton bound states using numerical and analytical methods.

Contribution

It introduces a coupled model for BEC and TG gases, derives an immiscibility condition, and systematically characterizes various interface states including domain walls, bubble drops, and solitons.

Findings

Families of domain wall states are identified.

Bubble drops exist as TG drops in BEC background.

Bound states of bright and dark solitons are found.

Abstract

We consider one-dimensional mixtures of an atomic Bose-Einstein condensate (BEC) and Tonks- Giradeau (TG) gas. The mixture is modeled by a coupled system of the Gross-Pitaevskii equation for the BEC and the quintic nonlinear Schroedinger equation for the TG component. An immiscibility condition for the binary system is derived in a general form. Under this condition, three types of BEC-TG interfaces are considered: domain walls (DWs) separating the two components; bubble-drops (BDs), in the form of a drop of one component immersed into the other (BDs may be considered as bound states of two DWs); and bound states of bright and dark solitons (BDSs). The same model applies to the copropagation of two optical waves in a colloidal medium. The results are obtained by means of systematic numerical analysis, in combination with analytical Thomas-Fermi approximations (TFAs). Using both methods, families of DW states are produced in a generic form. BD complexes exist solely in the form of a TG drop embedded into the BEC background. On the contrary, BDSs exist as bound states of TG bright and BEC dark components, and vice versa.