Fig. 2: Microwave transmission in the paramagnetic regime.
From: Waveguide quantum electrodynamics at the onset of spin-spin correlations
a Two- dimensional plot of the normalized microwave transmission ∣S21∣ of a superconducting wave guide coupled to a DPPH polycrystalline pellet, measured at T = 2 K. The insets show the shape of both the absorption (reflection) amplitude ∣S21∣ (∣S11∣) and its phase φ21 (φ11) with their corresponding fits based on Eq. (1), from which we determine the collective spin-photon coupling G and the decay rate Γ. b Values for G and Γ obtained from these fits as a function of magnetic field. The lines are least-square fits based on Eq. (2), for G, and on a constant function Γ/2π ≃ 14 MHz. The inset shows the maximum transmission visibility η as a function of magnetic field (open dots) and the prediction derived from Eq. (1) (solid line).
