Polarons and molecules in a Fermi gas with orbital Feshbach resonance

We study the impurity problem in a gas of ¹⁷³Yb atoms near the recently discovered orbital Feshbach resonance. In an orbital Feshbach resonance, atoms in the electronic ground state ^S1₀ interact with those in the long-lived excited ^P3₀ state with magnetically tunable interactions. We consider an impurity atom with a given hyperfine spin in the ^P3₀ state interacting with a single-component Fermi sea of atoms in the ground ^S1₀ 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. As the magnetic field decreases, a molecular state becomes the ground state of the system. We show that a polaron to molecule transition exists in ¹⁷³Yb 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.