Quantum Geometry and Flat Band Bose-Einstein Condensation

Aleksi Julku; Georg M. Bruun; Päivi Törmä

doi:10.1103/PhysRevLett.127.170404

Quantum Geometry and Flat Band Bose-Einstein Condensation

Aleksi Julku, Georg M. Bruun, Päivi Törmä

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Abstract

We study the properties of a weakly interacting Bose-Einstein condensate (BEC) in a flat band lattice system by using the multiband Bogoliubov theory and discover fundamental connections to the underlying quantum geometry. In a flat band, the speed of sound and the quantum depletion of the condensate are dictated by the quantum geometry, and a finite quantum distance between the condensed and other states guarantees stability of the BEC. Our results reveal that a suitable quantum geometry allows one to reach the strong quantum correlation regime even with weak interactions.

Original language	English
Article number	170404
Number of pages	6
Journal	Physical Review Letters
Volume	127
Issue number	17
DOIs	https://doi.org/10.1103/PhysRevLett.127.170404
Publication status	Published - 22 Oct 2021
MoE publication type	A1 Journal article-refereed

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10.1103/PhysRevLett.127.170404

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abstract = "We study the properties of a weakly interacting Bose-Einstein condensate (BEC) in a flat band lattice system by using the multiband Bogoliubov theory and discover fundamental connections to the underlying quantum geometry. In a flat band, the speed of sound and the quantum depletion of the condensate are dictated by the quantum geometry, and a finite quantum distance between the condensed and other states guarantees stability of the BEC. Our results reveal that a suitable quantum geometry allows one to reach the strong quantum correlation regime even with weak interactions.",

author = "Aleksi Julku and Bruun, {Georg M.} and P{\"a}ivi T{\"o}rm{\"a}",

note = "Funding Information: Academy of Finland Jenny ja Antti Wihurin Rahasto National Science Foundation Funding Information: We thank Long Liang and Menderes Iskin for useful discussions. A. J. and P. T. acknowledge support by the Academy of Finland under Projects No. 303351, No. 307419, and No. 327293. A. J. acknowledges financial support from the Jenny and Antti Wihuri Foundation. This research was supported in part by the National Science Foundation under Grant No. PHY-1748958. Publisher Copyright: {\textcopyright} 2021 American Physical Society",

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AB - We study the properties of a weakly interacting Bose-Einstein condensate (BEC) in a flat band lattice system by using the multiband Bogoliubov theory and discover fundamental connections to the underlying quantum geometry. In a flat band, the speed of sound and the quantum depletion of the condensate are dictated by the quantum geometry, and a finite quantum distance between the condensed and other states guarantees stability of the BEC. Our results reveal that a suitable quantum geometry allows one to reach the strong quantum correlation regime even with weak interactions.

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Quantum Geometry and Flat Band Bose-Einstein Condensation

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