The short-range three-body phase and other issues impacting the observation of Efimov physics in ultracold quantum gases

TL;DR

This paper investigates the challenges in observing Efimov physics in ultracold gases, highlighting the influence of realistic potentials, short-range effects, and the limitations of current theoretical models in predicting three-body phenomena.

Contribution

It provides a detailed numerical analysis of three-boson systems with realistic potentials, clarifying the connection between scattering lengths and Efimov features, and emphasizing the role of short-range three-body physics.

Findings

Realistic potentials can obscure Efimov signals at small scattering lengths.

Universal connection between positive and negative scattering lengths occurs only across a pole.

Efimov feature spacing deviates from the ideal geometric progression at accessible scattering lengths.

Abstract

We discuss several issues important for experimentally observing Efimov physics in ultracold quantum gases. By numerically solving the three-boson Schr\"odinger equation over a broad range of scattering lengths and energies, and by including model potentials with multiple bound states, we address the complications of relating experimental observations to available analytic expressions. These more realistic potentials introduce features that can mask the predicted Efimov physics at small scattering lengths. They also allow us to verify that positive and negative scattering lengths are universally connected only across a pole, not across a zero. Additionally, we show that the spacing between Efimov features for the relatively small scattering lengths accessible experimentally fail to precisely follow the geometric progression expected for Efimov physics. Finally, we emphasize the importance of the short-range three-body physics in determining the position of Efimov features and show that theoretically reproducing two-body physics is not generally sufficient to predict three-body properties quantitatively.