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arXiv · 2104.14257

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 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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Aleksi Julku, Georg M. Bruun, Päivi Törmä. 2021-10-01. Quantum geometry and flat band Bose-Einstein condensation. https://doi.org/10.1103/physrevlett.127.170404

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