LSCO fluctuations: what THz conductivity resolves

Bilbro and colleagues studied eight LSCO films, $x=0.09$–$0.25$. Their THz conductivity criterion places the fluctuation onset 5–16 K above $T_c$. They determine onset from the curvature of $\omega\sigma_2$ at 0.8 THz. This is a probe-dependent transport result, not exclusion of all higher-temperature pairing. Figure 3 assigns $T_c=23.5$ K to $x=0.25$.

The angular-rate form is $\Omega=\alpha k_BT/\hbar$; the plotted cyclic frequency is $\Omega/(2\pi)=\alpha k_BT/h$. Methods set $\alpha=0.4$ to the mean after a loss-peak normalization gives a roughly 40% spread. It is not a precision universal constant. The authors cannot distinguish normal-state masking from intrinsically linear-in-temperature fluctuations.

An editorial comparison should record the sample, probe frequency, onset criterion, background treatment and rate definition before comparing a transport result with a magnetic signal. A common temperature dependence alone does not identify a common mechanism.

Keep these film measurements separate from interface localization. This note is not a new transition-temperature record in the material-condition catalogue.

This note covers study 5 of the inherited ten-study series. Studies 2 and 9 have separate interface coverage; study 3 has a magnetic-excitation note, and the other six remain pending. The provenance records partial coverage of both source notes.

Use the archive submission date for this source version. Its printed typesetting date is not the journal publication date. The arXiv distribution license is not a general permission to reproduce the paper.