Instability and stratification of a two-component Bose-Einstein condensate in a trapped ultracold gas

Abstract

The thermodynamic stability of a trapped Bose gas with a two-component condensate, e.g., a gas of atoms in two distinct hyperfine states or a binary gaseous mixture, is considered on the basis of modified Gross-Pitaevskii equations. Under certain conditions the system becomes unstable with respect to stratification, i.e., to spatial separation between the two condensates. One condensate assumes a donutlike spatial distribution, while the other retains a centered distribution. Possible applications of the theory to recent experimental data on two overlapping condensates in 87 Rb are discussed.

Modulational instability of two-component Bose-Einstein condensates in an optical lattice

“…which agrees with the usual expression obtained from continuous NLS equations [14][15][16] The MI condition for the two-component BECs are determined by the condition: ǫ q (ǫ q + ∆ σ ) < 0. For the miscible BECs with Λ 2 12 < Λ 1 Λ 2 , the MI occurs for cos(k) < 0 and ǫ q + ∆ σ > 0.…”

Macroscopic quantum tunneling of two-component Bose-Einstein condensates

“…Thus we need to know detailed information about the stationary state of this system. The structure of the ground state has been studied by solving two coupled Gross-Pitaevskii equations (GPEs) analytically or numerically [4,5,6,7,8,9,10,11,12,13,14,15]. The stationary solution of the GPEs gives the density profile of the condensate characterized by the parameters of the system-trapping frequencies, the number of atoms of each component, and three s-wave scattering lengths, a 1 , a 2 , and a 12 , which represent the interactions between like and unlike components.…”

Cold bosons in optical lattices

“…The simplest case, studied long time ago [197][198][199][200][201], is the mixture of several components of Bose particles with different masses and different interactions with each other. Another example is the mixture of atoms with different spins or hyperfine states [202].…”

“…Depending on the kind of the interactions in a multicomponent system, the latter can be unstable with reference to the component stratification [198][199][200][201], when the components spatially separate from each other, rendering the system to a set of single-component parts.…”