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Condensed ground states of frustrated Bose-Hubbard models

Möller, Gunnar, Cooper, N R (2010) Condensed ground states of frustrated Bose-Hubbard models. Physical Review A, 82 (6). 063625. ISSN 1050-2947. E-ISSN 1094-1622. (doi:10.1103/PhysRevA.82.063625)

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http://dx.doi.org/10.1103/PhysRevA.82.063625

Abstract

We study theoretically the ground states of two-dimensional Bose-Hubbard models which are frustrated by gauge fields. Motivated by recent proposals for the implementation of optically induced gauge potentials, we focus on the situation in which the imposed gauge fields give rise to a pattern of staggered fluxes of magnitude ? and alternating in sign along one of the principal axes. For ?=1/2 this model is equivalent to the case of uniform flux per plaquette n?=1/2, which, in the hard-core limit, realizes the “fully frustrated” spin-1/2 XY model. We show that the mean-field ground states of this frustrated Bose-Hubbard model typically break translational symmetry. Given the presence of both a non-zero superfluid fraction and translational symmetry breaking, these phases are supersolid. We introduce a general numerical technique to detect broken symmetry condensates in exact diagonalization studies. Using this technique we show that, for all cases studied, the ground state of the Bose-Hubbard model with staggered flux ? is condensed, and we obtain quantitative determinations of the condensate fraction. We discuss the experimental consequences of our results. In particular, we explain the meaning of gauge invariance in ultracold-atom systems subject to optically induced gauge potentials and show how the ability to imprint phase patterns prior to expansion can allow very useful additional information to be extracted from expansion images.

Item Type: Article
DOI/Identification number: 10.1103/PhysRevA.82.063625
Uncontrolled keywords: Physics of Quantum Materials
Subjects: Q Science > QC Physics > QC173.45 Condensed Matter
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Gunnar Moller
Date Deposited: 05 Dec 2017 15:07 UTC
Last Modified: 05 Jul 2019 10:30 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/55543 (The current URI for this page, for reference purposes)
Möller, Gunnar: https://orcid.org/0000-0001-8986-0899
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