Recombination in the universal four-fermion system

• Main Author: A. Deltuva
• Format: Article
• Language: English
• Published: Elsevier 2021-09-01
• Series: Physics Letters B
• Subjects: Four-particle scattering; Fermionic dimer; Recombination; Universality
• Online Access: http://www.sciencedirect.com/science/article/pii/S0370269321005396

In the systems of spin 12 fermions with resonant S-wave interactions supporting only weakly bound dimers the antisymmetry forbids recombination of three (or more) fermions at zero energy. However, the fermion-fermion-dimer recombination is only partially suppressed. It is studied in the framework of momentum-space integral equations for the four-particle transition operators. In the vicinity of the unitary limit the fermion-fermion-dimer recombination rate, rescaled to build dimensionless quantity, is found to be linear in the effective range parameter, enabling a simple and accurate parametrization as well as evaluation of finite-range effects for any potential model. This feature makes the present results very useful in benchmarking different methods for three-cluster breakup and recombination calculations in four-particle systems. The interplay of the three-fermion and fermion-fermion-dimer recombination processes and their consequences for ultracold mixtures of fermions and dimers is discussed.