title: Two-dimensional Bose gases near resonance: competing two-body and three-body effects.
abstract: We report in this Letter the results of our investigation of 2D Bose gases beyond the dilute limit emphasizing the role played by three-body scattering events. We demonstrate that a competition between three-body attractive interactions and two-body repulsive forces results in the chemical potential of 2D Bose gases to exhibit a maximum at a critical scattering length beyond which these quantum gases possess a negative compressibility. For larger scattering lengths, the increasingly prominent role played by three-body attractive interactions leads to an onset instability at a second critical value. The three-body effects studied here are universal, fully characterized by the effective 2D scattering length a(2D) (or the size of the 2D bound states) and are, in comparison to the 3D case, independent of three-body ultraviolet physics. We find, within our approach, the ratios of the contribution to the chemical potential due to three-body interactions to the one due to two-body to be 0.27 near the maximum of the chemical potential and 0.73 in the vicinity of the onset instability.
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada.
authors.forename: Mohammad S
authors.initials: MS
authors.lastname: Mashayekhi
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada.
authors.forename: Jean-Sébastien
authors.initials: JS
authors.lastname: Bernier
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Borzov
authors.affiliation: Institute for Quantum Optics and Quantum Information, Austrian Academy of Sciences, A-6020 Innsbruck, Austria.
authors.forename: Jun-Liang
authors.initials: JL
authors.lastname: Song
authors.affiliation: Department of Physics and Astronomy, University of British Columbia, Vancouver V6T 1Z1, Canada.
authors.forename: Fei
authors.initials: F
authors.lastname: Zhou