Fig. 1: Concept of the experiment.
From: Density-wave ordering in a unitary Fermi gas with photon-mediated interactions
a, A strongly interacting Fermi gas trapped inside a high-finesse optical resonator is illuminated by a standing-wave pump laser with wave vector kp, polarized along the direction of the magnetic field B, which intersects the axis of the cavity mode (x direction) with wave vector kc at an angle of 18°. The pump beam couples dispersively to atomic motion. Off-resonant scattering of pump photons by the atoms into the cavity mode and vice versa leads to an effective infinite-range interaction between atoms. Above a critical strength, the infinite-range interaction results in a superradiant phase transition to a DW-ordered state with spatial modulation at 2π/k−. b, In the left panel, photon scattering from the pump into the cavity and vice versa via the atoms imparts momentum kicks k± = kc ± kp onto the latter, displacing the Fermi surface. In the right panel, since ∣k−∣ < kF, the photon-mediated interactions induce particle-hole excitations at the Fermi surface in addition to Cooper pairing arising from the contact interactions.
