Parallel conduction and Planckian scattering in FeTeSe

Romero and colleagues analyzed complex terahertz conductivity alongside DC resistance in two FeTe1−xSex films. Their model separates a narrow Drude response from a much broader background. Within the measured frequency window, the narrow-channel width is approximately linear in temperature, while the total resistance need not be. The inferred condensate weight is mainly associated with that channel. This is an author-version interpretation, not a unique determination of the pairing interaction.

For a Drude denominator $\Gamma-i\nu$, both variables use ordinary frequency. The corresponding pole decay rate is $\gamma=2\pi\Gamma$. Thus $\Gamma=\alpha k_BT/h$ and $\gamma=\alpha k_BT/\hbar$ express the same coefficient after conversion. The inherited reading note mixed these conventions. Its numerical expressions must not be copied unchanged.

As a separate local illustration, take fixed $S>0$, $\sigma_0\geq0$, $c>0$, $\Gamma_0\geq0$ and $T>0$:

$\sigma_{\rm DC}=\sigma_0+\frac{S}{\Gamma_0+cT},\qquad \rho_{\rm DC}=\frac{\Gamma_0+cT}{S+\sigma_0(\Gamma_0+cT)}.$

Differentiation gives $d\rho_{\rm DC}/dT=cS/[S+\sigma_0(\Gamma_0+cT)]^2$. A linear narrow-channel rate therefore need not give linear total resistivity. When $\sigma_0=0$, this model does recover a linear resistivity. The approximation $\sigma_{\rm DC}=a+b/T$ additionally neglects $\Gamma_0$ and assumes sufficiently constant amplitudes. This algebra is not a fit to the experimental data.

The broad contribution is not resolved as an independent complete Drude peak. Its microscopic origin and a unique relaxation coefficient are therefore not established by this fit. The manuscript discusses nematic pairing qualitatively and leaves the mechanism open. Its printed missing-area prefactor requires comparison with the final paper and normalization before precise condensate fractions are imported. No third-party figures or full text are reproduced here.