Quantum Geometry and Flat Band Bose-Einstein Condensation

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.

Automated summary

Through the multiband Bogoliubov theory, we have studied the properties of weakly interacting Bose-Einstein condensates in flat band lattice systems and discovered fundamental connections to the underlying quantum geometry. Suitable quantum geometry allows for reaching strong quantum correlations even with weak interactions.