Two-dimensional Bose gases near resonance: universal three-body effects

TL;DR

This paper investigates the universal three-body effects in two-dimensional Bose gases near resonance, revealing how three-body attractions influence stability and lead to instabilities, with results characterized by the effective 2D scattering length.

Contribution

It provides a detailed analysis of three-body effects in 2D Bose gases near resonance, highlighting their universality and impact on stability and chemical potential behavior.

Findings

Chemical potential exhibits a maximum at a critical scattering length.

Onset instability occurs at a second critical scattering length.

Three-body effects contribute significantly to the chemical potential near critical points.

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.