Publication: Low-energy behavior of strongly interacting bosons on a flat-band lattice above the critical filling factor
Authors
Phillips, Lawrence G. ; De Chiara, Gabriele ; Ohberg, Patrik ; Valiente Cifuentes, Manuel
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Publisher
American Physical Society
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DOI
https://doi.org/10.1103/PhysRevB.91.054103
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info:eu-repo/semantics/article
Description
© 2015 American Physical Society. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Published Manuscript, version of a Published Work that appeared in final form in Physical Review B (condensed matter and materials physics). To access the final edited and published work see https://doi.org/10.1103/PhysRevB.91.054103
Abstract
Bosons interacting repulsively on a lattice with a flat lowest band energy dispersion may, at sufficiently small filling factors, enter into a Wigner-crystal-like phase. This phase is a consequence of the dispersionless nature of the system, which in turn implies the occurrence of single-particle localized eigenstates. We investigate one of these systems—the sawtooth lattice—filled with strongly repulsive bosons at filling factors infinitesimally above the critical point where the crystal phase is no longer the ground state. We find, in the hard-core limit, that the crystal retains its structure in all but one of its cells, where it is broken. The broken cell corresponds to an exotic kind of repulsively bound state, which becomes delocalized. We investigate the excitation spectrum of the system analytically and find that the bound state behaves as a single particle hopping on an effective lattice with reduced periodicity, and is therefore gapless. Thus, the addition of a single particle to a flat-band system at critical filling is found to be enough to make kinetic behavior manifest.
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Citation
Physical Review B, Vol. 91, 054103 (2015)
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