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Beyond-mean-field effects in ultracold gases

Abstract : Ultracold gases are well controllable quantum systems that are described by a set of few parameters. The idea to look at systems with partially attractive and repulsive forces, fine-tuned to an approximate overall cancellation of the mean-field term, provide an interesting platform for studying various beyond-mean-field phenomena, remarkable recent examples being quantum droplets and dipolar supersolids. In this manuscript, we take a step towards understanding the phase diagram of the 1D Bose-Bose mixture with attractive interspecies and repulsive intraspecies contact interactions. We address the one-dimensional three-body problem with two- and three-body interactions that we solve analytically. Then, we develop the perturbation theory for systems with a weak two-body potential interaction, where the attractive and repulsive parts compensate each other. We calculate in every dimension the leading nonpairwise contribution, which represents an effective three-body interaction. We apply this result particularly to tilted dipoles in quasi-low-dimensional geometries. Interestingly, we show the consistency of this few-body perturbative approach with the Bogoliubov one. Finally, we present a way to engineer an effective three-body force to stabilize some bosonic systems near a narrow Feshbach resonance.
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Submitted on : Wednesday, December 1, 2021 - 9:26:07 PM
Last modification on : Tuesday, January 4, 2022 - 6:41:31 AM


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  • HAL Id : tel-03409873, version 2



Alexandre Pricoupenko. Beyond-mean-field effects in ultracold gases. Quantum Gases [cond-mat.quant-gas]. Université Paris-Saclay, 2021. English. ⟨NNT : 2021UPASP070⟩. ⟨tel-03409873v2⟩



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