A Universal Trimer in a Three-Component Fermi Gas

TL;DR

This paper explains the magnetic field dependence of three-body loss in a three-component ultracold fermion gas by identifying a universal trimer state, adapting bosonic three-body theory to fermions, and considering trimer lifetime variations.

Contribution

It introduces a novel adaptation of bosonic three-body theory to three distinguishable fermions and emphasizes the importance of trimer lifetime variation in explaining experimental data.

Findings

Universal trimer state explains loss rates across magnetic fields

Adapted theory matches experimental observations

Trimer lifetime variation is crucial for understanding decay rates

Abstract

We show that the recently measured magnetic field dependence of three-body loss in a three-component mixture of ultracold $^6$Li atoms [1,2] can be explained by the presence of a universal trimer state. Previous work suggested a universal trimer state as a probable explanation, yet failed to get good agreement between theory and experiment over the whole range of magnetic fields. For our description we adapt the theory of Braaten and Hammer [3] for three identical bosons to the case of three distinguishable fermions by combining the three scattering lengths $a_{12},$ $a_{23}$ and $a_{13}$ between the three components to an effective interaction parameter $a_m$. We show that taking into account a magnetic field variation of the lifetime of the trimer state is essential to obtain a complete understanding of the observed decay rates.