Attractive ultracold bosons in a necklace optical lattice

Year: 2005

Authors: Buonsante P., Penna V., Vezzani A.

Autors Affiliation: Dipartimento di Fisica, Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino, Italy; Dipartimento di Fisica, Università degli Studi di Parma and C.N.R.-I.N.F.M., Parco Area delle Scienze 7/a, I-43100 Parma, Italy

Abstract: We study the ground-state properties of the Bose-Hubbard model with attractive interactions on an M-site one-dimensional periodic-necklacelike-lattice, whose experimental realization in terms of ultracold atoms is promised by a recently proposed optical trapping scheme, as well as by the control over the atomic interactions and tunneling amplitudes granted by well-established optical techniques. We compare the properties of the quantum model to a semiclassical picture based on a number-conserving su(M) coherent state, which results in a set of modified discrete nonlinear Schrodinger equations. We show that, owing to the presence of a correction factor ensuing from number conservation, the ground-state solution to these equations provides a remarkably satisfactory description of its quantum counterpart not only-as expected-in the weak-interaction, superfluid regime, but even in the deeply quantum regime of large interactions and possibly small populations. In particular, we show that in this regime, the delocalized, Schrodinger-cat-like quantum ground state can be seen as a coherent quantum superposition of the localized, symmetry-breaking ground state of the variational approach. We also show that, depending on the hopping to interaction ratio, three regimes can be recognized both in the semiclassical and quantum picture of the system.

Journal/Review: PHYSICAL REVIEW A

Volume: 72 (4)      Pages from: 043620-1  to: 043620-10

KeyWords: ultracold atoms; optical lattices; attractive interactions; Schroedinger cat;
DOI: 10.1103/PhysRevA.72.043620

Citations: 40
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