Polarons and Molecules in a Fermi Gas with Orbital Feshbach Resonance

TL;DR

This paper investigates impurity behavior in a $^{173}$Yb Fermi gas near an orbital Feshbach resonance, revealing a transition from polaron to molecule states and proposing detection via Raman spectroscopy.

Contribution

It demonstrates the existence of a polaron-molecule transition in $^{173}$Yb atoms near the orbital Feshbach resonance, highlighting the role of spin-exchange interactions.

Findings

Polaron to molecule transition occurs near the resonance.

Spin-flipping processes influence polaron and molecule formation.

Raman spectroscopy can detect the transition.

Abstract

We study the impurity problem in a gas of $^{173}$Yb atoms near the recently discovered orbital Feshbach resonance. In an orbital Feshbach resonance, atoms in the electronic ground state $^1S_0$ interact with those in the long-lived excited $^3P_0$ state with magnetically tunable interactions. We consider an impurity atom with a given hyperfine spin in the $^3P_0$ state interacting with a single-component Fermi sea of atoms in the ground $^1S_0$ manifold. Close to the orbital Feshbach resonance, the impurity can induce collective particle-hole excitations out of the Fermi sea, which can be regarded as the polaron state. While as tuning toward the BEC regime of the resonance, a molecular state becomes the ground state of the system. We show that a polaron to molecule transition exists in $^{173}$Yb atoms close to the orbital Feshbach resonance. Furthermore, due to the spin-exchange nature of the orbital Feshbach resonance, the formation of both the polaron and the molecule involve spin-flipping processes with interesting density distributions among the relevant hyperfine spin states. We show that the polaron to molecule transition can be detected using Raman spectroscopy.