Van der Waals universality near a quantum tricritical point

TL;DR

This paper investigates the universal behavior of the three-body scattering hypervolume near a quantum tricritical point, revealing how it influences the thermodynamics and excitations of Bose-Einstein condensates, especially quantum droplets.

Contribution

It demonstrates the universality of the three-body scattering hypervolume in the weakly interacting regime near a quantum tricritical point, linking microscopic scattering to macroscopic properties.

Findings

Real part of D behaves universally for |a|/r_vdW ≤ 1

Hard-spherelike collisions dominate elastic three-body scattering

Predictions for quantum droplets stabilized by three-body interactions

Abstract

We study the three-body scattering hypervolume $D$ of atoms whose scattering length $a$ is on the order of or smaller than the typical range $r_{\mathrm{vdW}}$ of the van der Waals attraction. We find that the real part of $D$ behaves universally in this weakly interacting regime ($|a|/r_{\mathrm{vdW}}\lesssim 1$) in the absence of trimer resonances. This universality originates from hard-spherelike collisions that dominate elastic three-body scattering. We use this result to make quantitative predictions for the thermodynamics and elementary excitations of an atomic Bose-Einstein condensate in the vicinity of a quantum tricritical point, including quantum droplets stabilized by effective three-body interactions.