The mixing-demixing phase diagram of ultracold heteronuclear mixtures in a ring trimer

Abstract

We derive the complete mixing-demixing phase-diagram relevant to a bosonic binary mixture confined in a ring trimer and modeled within the Bose-Hubbard picture. The mixing properties of the two quantum fluids, which are shown to be strongly affected by the fragmented character of the confining potential, are evaluated by means of a specific indicator imported from Statistical Thermodynamics and are shown to depend only on two effective parameters incorporating the asymmetry between the heteronuclear species. To closely match realistic experimental conditions, our study is extended also beyond the pointlike approximation of potential wells by describing the systems in terms of two coupled Gross-Pitaevskii equations. The resulting mean-field analysis confirms the rich scenario of mixing-demixing transitions of the mixture and also constitutes an effective springboard towards a viable experimental realization. We additionally propose an experimental realization based on a realistic optical-tweezers system and on the bosonic mixture 23 Na + 39 K, thanks to the large tunability of their intra- and inter-species scattering lengths.

Quantum-Granularity Effect in the Formation of Supermixed Solitons in Ring Lattices

“…come into play [19,21]. It is to be noted, in this regard, that, in the limit of large boson populations, not only the inherently discrete variables Nj and Mj can be replaced with their continuous counterparts xj and yj, but also the contribution of tunnelling terms in potential (2) can be neglected (recall that tunnelling energy scales as Nc, while intra-and interspecies coupling energies scale as N 2 c , where c = a, b).…”

“…In particular, mixing-demixing transitions have been thoroughly described, in the case of small-size lattices, for repulsive [14,17,18,19,20] and attractive [21] interspecies couplings. These analyses have highlighted rather complex quantum phase diagrams where various phases, differing in the degree of mixing and localization of the two bosonic species, are recognizable.…”

“…Mixing-demixing and mixing-supermixing transitions in ultracold bosonic mixtures, which involve the localization of the condensed species in different sites of the lattice, have also been shown to be strongly associated to the presence of criticalities in a number of quantum indicators. The latter include, but are not limited to, the functional dependence of the ground state energy on model parameters, the energy fingerprint (constituted by the structure of the first excited energy levels), and the degree of entanglement between the bosonic species of the mixture [23,18,19,21,14].…”

A Dual-Species Bose-Einstein Condensate with Attractive Interspecies Interactions

“…Ultracold atomic mixtures, formed by atoms of the same species in different spin states, or as different isotopes or elements, enable us to address a wide variety of problems in many-body physics. They have been largely used to investigate phase-transitions [1][2][3][4], multi-component superfluidity [5][6][7], topological defects [8][9][10], magnetism [11][12][13], ultracold chemistry [14] and impurity and polaron physics [15][16][17]. Most of these phenomena are accessible thanks to the ability to control the sign and strength of interactions, opening the way to the study of unconventional matter phases.…”

Immiscible and miscible states in binary condensates in the ring geometry

“…In addition to Bose-Bose mixtures of different isotopes and atomic species [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18], experimentalists have in the past few years created condensates with a spin degree of freedom [19], also implementing spin-orbit coupling which gives rise to exciting new states [20][21][22][23][24]; moreover, recent achievements have led to the generation of doubly-superfluid Bose-Fermi mixtures [25], in which both components are condensed, a state so far inaccessible in other settings (such as superfluid helium). Although the stability and phase diagrams of such systems have been extensively studied in the course of more than 20 years , even simple hetero-species binary mixtures still reveal unexpected features, such as the role of the trap sag, atom number and kinetic energy contribution to the extent of miscibility in trapped configurations [42,50,52], and nontrivial effects of the expansion on the mixtures' dynamics [51,53].…”