Efimov physics from the functional renormalization group

TL;DR

This paper uses the functional renormalization group method to analyze Efimov physics in few-body systems, explaining experimental loss rates and connecting to many-body phenomena like BCS-BEC crossover.

Contribution

It applies the modern functional renormalization group formalism to Efimov physics, providing new insights into three-body loss rates and the relation to many-body states.

Findings

Explains three-body loss rates in ultracold Fermi gases.

Identifies a limit cycle in the renormalization group flow.

Discusses the connection to BCS-BEC crossover and trion phases.

Abstract

Few-body physics related to the Efimov effect is discussed using the functional renormalization group method. After a short review of renormalization in its modern formulation we apply this formalism to the description of scattering and bound states in few-body systems of identical bosons and distinguishable fermions with two and three components. The Efimov effect leads to a limit cycle in the renormalization group flow. Recently measured three-body loss rates in an ultracold Fermi gas $^6$Li atoms are explained within this framework. We also discuss briefly the relation to the many-body physics of the BCS-BEC crossover for two-component fermions and the formation of a trion phase for the case of three species.