Influence of the Intraspecies Scattering Length on the Three-Body Parameter in Efimov-Unfavored Systems*

Although the Efimov effect is primarily known for three identical bosons, it also occurs in three-body heteronuclear systems (BBX) with at least two resonant pairs (i.e., the interspecies scattering length a_BX = ∞) [1,2]. Efimov resonances associated with heteronuclear trimers have been observed in ultracold two-species gases near an interspecies Feshbach resonance [3,4]. However, in most studies, the intraspecies scattering length a_BB has been treated as a background parameter with no significant influence on the locations of the Efimov resonances a_-⁽ⁿ⁾ (in a_BX) or, in turn, on the three-body parameter (3BP). In Efimov-unfavored systems (m_B < m_X), a_BB is expected to play a crucial role due to the large discrepancy between the Efimov scaling parameters for two (s₀) and three (s₀^*) resonant pairs [2], highlighting the importance of the intraspecies interaction. This work investigates the dependence of the Efimov resonances a_-⁽ⁿ⁾, particularly the 3BP a_-⁽⁰⁾, on a_BB in Efimov-unfavored systems. It is found that both the magnitude and sign of the intraspecies scattering length a_BB can drastically impact the 3BP in these systems.

 

[1] V. Efimov, Nuclear Physics A 210, 157 (1973).

[2] Y. Wang, J. Wang, J. P. D’Incao, and C. H. Greene, Phys. Rev. Lett. 109, 243201 (2012).

[3] J. Ulmanis, S. H¨afner, R. Pires, F. Werner, D. S. Petrov, E. D. Kuhnle, and M. Weidem¨uller, Phys. Rev. A 93, 022707 (2016).

[4] A. Y. Chuang, H. Q. Bui, A. Christianen, Y. Zhang, Y. Ni, D. Ahmed-Braun, C. Robens, and M. W. Zwierlein, arXiv:2411.04820, (2024).