Quantum correlations and spatial localization in one-dimensional ultracold bosonic mixtures

• Published in: New journal of physics 2014-10, Vol.16 (10), p.103004-17
• Main Authors: García-March, M A, Juliá-Díaz, B, Astrakharchik, G E, Busch, Th, Boronat, J, Polls, A
• Format: Article
• Language: English
• Subjects: Atomic properties; atoms; Balancing; Binary mixtures; Bose-Einstein condensate; Bose-Einstein condensation; bosonic mixtures; Bosons; Condensació de Bose-Einstein; confinement; Correlation; Density; Entanglement; Entropy; Extreme values; fermions; few-atom systems; Física; harmonic trap; impenetrable bosons; Interacting boson models; Interacting boson-fermion models; interacting bosons; Interaction parameters; macroscopic superpositions; Mathematical analysis; Mathematical models; Monte Carlo simulation; Parameter identification; Phase diagrams; Physics; separation; stability; Tonks-Girardeau gas; Àrees temàtiques de la UPC
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/16/10/103004

We present the complete phase diagram for one-dimensional binary mixtures of bosonic ultracold atomic gases in a harmonic trap. We obtain exact results with direct numerical diagonalization for a small number of atoms, which permits us to quantify quantum many-body correlations. The quantum Monte Carlo method is used to calculate energies and density profiles for larger system sizes. We study the system properties for a wide range of interaction parameters. For the extreme values of these parameters, different correlation limits can be identified, where the correlations are either weak or strong. We investigate in detail how the correlations evolve between the limits. For balanced mixtures in the number of atoms in each species, the transition between the different limits involves sophisticated changes in the one- and two-body correlations. Particularly, we quantify the entanglement between the two components by means of the von Neumann entropy. We show that the limits equally exist when the number of atoms is increased for balanced mixtures. Also, the changes in the correlations along the transitions among these limits are qualitatively similar. We also show that, for imbalanced mixtures, the same limits with similar transitions exist. Finally, for strongly imbalanced systems, only two limits survive, i.e., a miscible limit and a phase-separated one, resembling those expected with a mean-field approach.