Instabilities of a Bose-Einstein condensate with mixed nonlinear and linear lattices.

Hong, Jun; Wang, Chenhui; Zhang, Yongping · Phys Rev E · 2023

basic_science · Level V

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Abstract

Bose-Einstein condensates (BECs) in periodic potentials generate interesting physics on the instabilities of Bloch states. The lowest-energy Bloch states of BECs in pure nonlinear lattices are dynamically and Landau unstable, which breaks down BEC superfluidity. In this paper we propose to use an out-of-phase linear lattice to stabilize them. The stabilization mechanism is revealed by the averaged interaction. We further incorporate a constant interaction into BECs with mixed nonlinear and linear lattices and reveal its effect on the instabilities of Bloch states in the lowest band.