Precision Test of the Limits to Universality in Few-Body Physics

Area of Science:

• Atomic, Molecular, and Optical Physics
• Quantum Many-Body Systems
• Few-Body Physics

Background:

• Feshbach resonances are crucial for controlling interactions in ultracold atomic gases.
• Understanding three-body interactions is essential for explaining phenomena like the Efimov effect.
• Van der Waals universality provides a theoretical framework for predicting three-body phenomena.

Purpose of the Study:

• To precisely measure two- and three-body interactions in potassium-39 near a Feshbach resonance.
• To construct an accurate two-body model and determine scattering lengths with low uncertainty.
• To test the predictions of van der Waals universality for the Efimov ground state.

Main Methods:

• Precise measurements of dimer binding energies across three orders of magnitude.
• Development of a complete two-body coupled-channel model.
• Accurate determination of the scattering length map.
• Controlled experiments to precisely locate the Efimov ground state resonance.
• Precise control of sample temperature and density to minimize systematic effects.

Main Results:

• Determination of scattering lengths with unprecedented low uncertainty.
• Measurement of the ground Efimov resonance location at -14.05(17) times the van der Waals length (r_vdW).
• Significant deviation observed from the predicted value of -9.7r_vdW based on van der Waals universality.
• Successful accounting for the deviation using a refined multichannel three-body model.

Conclusions:

• The study demonstrates a deviation from van der Waals universality in the three-body system of potassium-39.
• A refined three-body model, incorporating precise two-body physics, successfully explains the observed deviation.
• The model also accurately predicts the Efimov inelasticity parameter, validating the refined approach.