The single-photon reflectivity in the system with one atom in the supercavity. The part between two red dashed vertical lines is the reflectivity peak. Here we choose the parameters as N = 31, Ω = 0.1, n₁ = 12 (antinode), ξ = 1, η = 0.01 while the atom is resonant with the 4-th eigen-mode of the supercavity with Δ = −2cos(4π/N + 1). In our calculation we fix the value of Δ and calculate the single-photon reflectivity R as a function of the momentum k of the incident photon. The horizontal label of the figure is δ/0.01, with δ = Δ − E_k.