Cell strong-coupling perturbative approach to the phase diagram of ultracold bosons in optical superlattices

Year: 2005

Authors: Buonsante P., Vezzani A.

Autors Affiliation: Dipartimento di Fisica, Politecnico di Torino; INFM and Dipartimento di Fisica, Università degli Studi di Parma

Abstract: The phase diagram of ultracold bosons in realistic optical superlattices is addressed via second-order cell strong coupling perturbative expansions for the Bose-Hubbard model describing the system. Taking advantage of the cell partition inherent in the complex periodic modulation of a superlattice, this technique allows for the description of the unusual loophole-shaped insulator domains that may occur in the phase diagram of the system, unlike the standard perturbative approach. Furthermore, comparisons with quantum Monte Carlo simulations show that our approach provides quantitatively satisfactory results at a significantly lower computational cost than brute force numerical methods. We explicitly consider the phase diagrams for two realistic 3-periodic optical superlattices. These show that many insulator domains exhibit an unusual reentrant character, which we discuss, and suggest that the quantum phase transition relevant to the loophole-shaped insulating domains does not require extreme experimental condition in order to be observed.

Journal/Review: PHYSICAL REVIEW A

Volume: 72 (1)      Pages from: 013614-1  to: 013614-9

KeyWords: ultracold atoms; optical lattices; superlattices; quantum phases;
DOI: 10.1103/PhysRevA.72.013614

ImpactFactor: 2.997
Citations: 32
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