Condensate fragmentation as a sensitive measure of the quantum many-body behavior of bosons with long-range interactions

Abstract

The occupation of more than one single-particle state and hence the emergence of fragmentation is a many-body phenomenon universal to systems of spatially confined interacting bosons. In the present study, we investigate the effect of the range of the interparticle interactions on the fragmentation degree of one- and two-dimensional systems. We solve the full many-body Schrödinger equation of the system using the recursive implementation of the multiconfigurational time-dependent Hartree for bosons method, R-MCTDHB. The dependence of the degree of fragmentation on dimensionality, particle number, areal or line density and interaction strength is assessed. It is found that for contact interactions, the fragmentation is essentially density independent in two dimensions. However, fragmentation increasingly depends on density the more long-ranged the interactions become. The degree of fragmentation is increasing, keeping the particle number $N$ fixed, when the density is decreasing as expected in one spatial dimension. We demonstrate that this remains, nontrivially, true also for long-range interactions in two spatial dimensions. We, finally, find that within our fully self-consistent approach, the fragmentation degree, to a good approximation, decreases universally as $N^{-1/2}$ when only $N$ is varied.

8 pages of RevTex4-1, 5 figures

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• Bogoliubov depletion of the fragmented condensate in the bosonic flux ladder
• Analysis of a trapped Bose-Einstein condensate in terms of position, momentum, and angular-momentum variance
• Beyond mean-field dynamics of ultra-cold bosonic atoms in higher dimensions: facing the challenges with a multi-configurational approach
• The multi-configurational time-dependent Hartree approach in optimized second quantization: imaginary time propagation and particle number conservation
• Condensates in annuli: Dimensionality of the variance
• Variance of a Trapped Bose-Einstein Condensate