The universality of the Efimov three-body parameter

TL;DR

This paper explores the universal behavior of the three-body parameter in Efimov physics, highlighting experimental findings and theoretical insights into the role of van der Waals interactions and nonadiabatic effects.

Contribution

It provides a theoretical analysis of the universality of the Efimov three-body parameter using hyperspherical formalism and emphasizes the multichannel and nonadiabatic aspects.

Findings

The three-body parameter shows universality across different atomic species.

Van der Waals interactions are crucial in understanding Efimov resonances.

Nonadiabatic effects significantly influence three-body physics.

Abstract

In this paper we discuss the recent discovery of the universality of the three-body parameter (3BP) from Efimov physics. This new result was identified by recent experimental observations in ultracold quantum gases where the value of the s-wave scattering length, $a=a_-$, at which the first Efimov resonance is created was found to be nearly the same for a range of atomic species --- if scaled as $a_-/r_{\rm vdW}$, where $r_{\rm vdW}$ is the van der Waals length. Here, we discuss some of the physical principles related to these observations that emerge from solving the three-body problem with van der Waals interactions in the hyperspherical formalism. We also demonstrate the strong three-body multichannel nature of the problem and the importance of properly accounting for nonadiabatic effects.