Universal Efimov spectra and fermionic doublets in highly mass-imbalanced cold-atom mixtures with van der Waals and dipole interactions

TL;DR

This paper investigates Efimov states in highly mass-imbalanced cold-atom mixtures with dipole interactions, revealing universal spectra and three-body parameters, especially in fermionic systems with characteristic doublets.

Contribution

It demonstrates the universality of Efimov spectra and three-body parameters in mass-imbalanced mixtures with dipole interactions, including fermionic doublets, supported by analytical and numerical results.

Findings

Efimov spectra are universal even with strong dipole interactions.

Fermionic systems exhibit a doublet of Efimov states due to anisotropy.

Universal ratios of three-body parameters are predicted for experimental systems.

Abstract

We study the Efimov states in highly mass-imbalanced three-body systems composed of two identical heavy atoms and one light atom, focusing on the Er-Er-Li and Dy-Dy-Li cold-atom mixtures with strong dipole-dipole interactions between the heavy atoms. By solving the Born-Oppenheimer equation for varying $s$-wave scattering lengths between the heavy and light atoms, we demonstrate for both bosonic and fermionic systems that the Efimov spectra and hence the three-body parameters are universal even with the dipole interaction comparable in strength to the van der Waals interaction. While the bosonic systems exhibit Efimov states only in the $M_z=0$ channel, the fermionic systems show a characteristic doublet of the Efimov states in the $M_z=0$ and $M_z = \pm 1$ channels due to the interplay of finite angular momentum and the anisotropy of the dipole interaction. Both numerical results and analytical formula obtained with the first-order perturbation show that the ratio of the three-body parameters between these two fermionic channels exhibits universality, particularly well in the limit of large mass imbalance. Leveraging this universality, we provide quantitative predictions for the values and ratios of the three-body parameters for experimentally relevant Er-Li and Dy-Li isotopes.