Fig. 1: Combining a unitary superfluid with a high-finesse cavity.

a A two-component Fermi gas is trapped in a crossed-dipole trap aligned onto the mode of a high-finesse optical cavity. A bias magnetic field oriented along the z-axis controls the interactions between the atoms. b Relevant energy levels of ⁶Li at 832 G including the frequencies of the probe laser and cavity resonance. In the experiment the detunings Δ_a and Δ_c are varied independently. c Doubly integrated density profiles, \({\overline{n}}_{\uparrow }\) and \({\overline{n}}_{\downarrow }\), along the longitudinal direction after transfer in an elongated trap, for 9.3(5) × 10⁴ and 6.0(3) × 10⁴ atoms in state \(\left|\uparrow \right\rangle\) (red) and \(\left|\downarrow \right\rangle\) (blue), respectively. The difference between the two doubly integrated profiles (orange) exhibits a plateau, characteristic of a superfluid core surrounded by a polarized shell. The grey dashed line is horizontal to guide the eye. Inset: absorption images (173 × 919 μm) taken along the z-axis of both spin states in the elongated trap after 300 μs time-of-flight. The peak line density is 244 μm⁻¹.