Extended Data Fig. 9: Equivalence of ϵ_∞ to two Lorentzians from (20) in low frequency limit.

(a), (b) are Fig. 2 (e), (f) from main text. (c), (d) σ_1,2 at 16 K being fit with 2 Drude + 2 Lorentzian model from (20) with the Lorentzians centered at 51 THz (low freq) and 120 THz (high freq). The equivalence of the two methods can be quantified by comparing the fit parameters of the two models. For our model (at 16 K) the narrow Drude has a scattering rate and spectral weight of Γ ≈ 1.2 THz and S ≈ 1.9 mΩ⁻¹ cm⁻¹ THz where as the broad Drude (σ₀) has a scattering rate and spectral weight orders of magnitude higher than the narrow Drude which we quantified by its DC intercept of σ₀ ≈ 1 mΩ⁻¹ cm⁻¹. The fit parameters from the two Lorentzian fit are qualitatively equivalent. The narrow Drude from the Lorentzian fit is parameterized by Γ_Narrow ≈ 0.9 THz and S_Narrow ≈ 1.5 mΩ⁻¹ cm⁻¹ THz. While the broad Drude from the two Lorentzian fit is parameterized by a DC intercept of σ₀ ≈ 1.2 mΩ⁻¹ cm⁻¹.