Quasiparticle excitations in Bose-Fermi mixtures

TL;DR

This paper investigates the excitation spectrum of a 3D Bose-Fermi mixture with tunable interactions, revealing Fermi liquid behavior and the impact of many-body reactions on phase transitions.

Contribution

It introduces a mean-field framework for quasiparticle excitations in Bose-Fermi mixtures with high spin degeneracy, highlighting novel chemical equilibrium conditions.

Findings

Fermi liquid description of low-lying excitations

Renormalization of bosonic chemical potential by many-body reactions

Modified condensation and superfluid-insulator transitions

Abstract

We analyze the excitation spectrum of a three-dimensional(3D) Bose-Fermi mixture with tunable resonant interaction parameters and high hyperfine spin multiplets. We focus on a 3-particle vertex describing fermionic and bosonic atoms which can scatter to create fermionic molecules or disassociate. For a single molecular level, in analogy to the single magnetic impurity problem we argue that the low lying excitations of the mean-field theory are described by the Fermi liquid picture with a quasiparticle weight and charge which is justified by a $1/N_\psi$ expansion, expected to be exact in the limit of infinite degeneracy (or very high fermionic spin) $N_\psi \to \infty$. Our emphasis is placed on the novel conditions for chemical equilibrium and how many-body chemical reactions renormalize the bosonic chemical potential, modifying condensation and superfluid-insulator transitions.