# LSCO fluctuations: what THz conductivity resolves

Read a finite-frequency fluctuation signal with its measurement window, rate normalization and unresolved alternatives.

## Review scope

Selected author-version text and figures, with methods and supplementary characterization; no raw-data reproduction or independent review.

- The final journal version has not been compared with this archived author version.
- This note covers study 5 only. Together with the interface and magnetic-excitation notes, four of ten inherited studies have limited coverage; six remain pending.
- A scoped author review does not establish full scientific acceptance.

## A conductivity window, not a universal pairing cutoff

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 $x=0.25$.

Evidence: experiment. Source relationship: direct-support. Sources: bilbro-author-v1.

## Keep the rate convention and scale uncertainty

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.

Evidence: experiment. Source relationship: direct-support. Sources: bilbro-author-v1.

## Use the measured observable in comparisons

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](/scwiki/library/cuprate-interface-layer-order). This note is not a new transition-temperature record in the material-condition catalogue.

Evidence: experiment. Source relationship: context-for-editorial-analysis. Sources: bilbro-author-v1.

## Coverage and source version

This note covers study 5 of the inherited ten-study series. Studies 2 and 9 have [separate interface coverage](/scwiki/library/cuprate-interface-layer-order); study 3 has a [magnetic-excitation note](/scwiki/library/dean-lsco-magnetic-excitations), 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.

Evidence: experiment. Source relationship: context-for-editorial-analysis. Sources: .

## Sources

bilbro-author-v1: L. S. Bilbro, R. Valdés Aguilar, G. Logvenov, O. Pelleg, I. Bozovic and N. P. Armitage. [Temporal correlations of superconductivity above the transition temperature in La2−xSrxCuO4 probed by terahertz spectroscopy](https://arxiv.org/abs/1110.2097v1). journal-article; Author version deposited 2011-10-10; arXiv:1110.2097v1, archived author version of Nature Physics 7, 298–302 (2011); not the version of record. Selected text pp1–6,8–9; pixels4,6,9 checked. Final-version comparison and raw data remain unreviewed. Source license: [arXiv distribution grant; not a public reuse license](https://arxiv.org/licenses/nonexclusive-distrib/1.0/license.html). Editorial wording and organization changed.

## Editorial corrections

- Sample temperature: Figure 3 instead labels23.5 K; retain specimen identity.
- Rate scale: Retain the stated scale-setting procedure and spread.
- Unsupported acquisition limit: Not verified in the selected source; do not transfer this acquisition claim.

## Provenance

papers/CROSS_D3_D11_BozovicInterface.md; commit 0a7c9d6696804ec26aa12f8eed68b55c9b3c0fcf; SHA-256 8f299055adac85ea95c5dca9a35c6939305162fa1c0f36e4a8f6d58211a7be83; partial-merge. Coverage: Section4.3: Bilbro temporal correlations only. Interface studies have a separate note; other CROSS comparisons remain pending.

papers/library/Bozovic_Cuprate-Interface-Series_READING_NOTES.md; commit 0a7c9d6696804ec26aa12f8eed68b55c9b3c0fcf; SHA-256 6c0b3484dbfe9831b95e8f1ad578c2889e9c88b5e25c6954bb09160df741f0ee; partial-merge. Coverage: Study section 5: Bilbro THz conductivity and its stated limits only. Six series studies and other CROSS claims remain pending.

Original concise synthesis and editorial analysis. No source figures or substantial paper text reproduced; arXiv redistribution rights are not assumed to grant public reuse.

Note ID: bilbro-thz-fluctuation-window. Revision: 8aac9dfeebbdfc5ad09e.