van der Waals Universality near a Quantum Tricritical Point
P. M. A. Mestrom, V. E. Colussi, T. Secker, G. P. Groeneveld, S. J. J. M. F. Kokkelmans
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_{vdW} of the van der Waals attraction. We find that the real part of D behaves universally in this weakly interacting regime (|a|/r_{vdW}≲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.