Bulk Charge Ordering in the CuO2 Plane of the Cuprate Superconductor YBa2Cu3O6.9 by High-Pressure NMR
Round 1
Reviewer 1 Report
Reichardt and coworkers report on 63Cu(2) and 17O NMR measurements in an optimally doped Y123 compound both as a function of temperature and pressure. They observe a clear change in the asymmetry and linewidth of the NMR spectra with decreasing temperature and increasing pressure which are associated with the development of a charge order. The manuscript is quite timely and its relevance stems also from the observation of charge ordering in an optimally doped high Tc superconductor. Nevertheless, while the authors arguing and basic findings seem correct I find the overall presentation difficult to be followed even by an expert in the field and it should be significantly revised. The point is that they present separately the findings for each nucleus, magnetic field orientation, temperature and pressure, while the reading would benefit from a view of the overall trend which can hardly be grasped after the first reading. Moreover, at the end it is not clear if out of the different microscopic configurations shown in Fig. 7 there is in fact one which is more likely or there are different configurations which are possible depending on the experimental conditions. If so why?
Minor remarks.
In Figs. 1 and 4 one can hardly see the dashed lines for the NQR and central line NMR spectra. What do the authors mean in the caption to Fig.4 when they write “magnetic variations contribute one time, the EFG variations contribute twice to the linewidth…”?
Author Response
Response to Reviewer 2
We thank the reviewer for the overall positive evaluation. Concerning the minor remarks, we have changed the figures as demanded. They are indeed much better now. Thank you.
We also changed the sentence in the caption to Fig. 4, it was not quite clear. Thank you.
According to the major criticism we agree, too, that this text was rather difficult to follow. While it is intended to be an experimental proof of an old conundrum, and as such it must almost be somewhat tedious, we made a number of changes to reduce the burden on the reader.
Mainly, we decided to add 5 paragraphs at the beginning of the RESULTS. With these, we lay out the strategy and with some examples already give an overview of what is expected. And we think that while reading the manuscript the reader can turn back to this part for guidance.
In addition, we implemented a number of smaller changes, especially in the INTRODUCTION.
We hope that satisfies the Reviewers wishes (there is no increase in overall space since Rev. 1 demanded to cut some discussion).
As to the charge density waves, since NMR is a bulk probe and we do not know whether we are missing up to 20 % of intensity, we cannot decide on wave scenarios.
Again, this paper is intended to decide whether an old explanation is right or wrong. Now, one can possibly learn more with dedicated experiments and literature data.
Thank you again.
J. Haase
Reviewer 2 Report
See attached report!
Comments for author File: 
Comments.pdf
Author Response
Response to Reviewer 1
We thank the reviewer for the positive evaluation.
We thank the Reviewer for pointing to the lacking identification of the panels in Fig. 4 and Fig. 5.
We have changed both captions accordingly.
Concerning the listing of possible connections with other methods, it is correct that we do not know whether these relations are reliable. We deleted – as demanded by Reviewer 1 - the text after “its effect … our conclusions”.
There is only one minor issue: It appears that Rev. 1 felt that a major change in language is recommended. We did ask a native speaker, but she did not fully share that opinion. Could that have been a mistake?
Thank you again.
J. Haase
Round 2
Reviewer 1 Report
The authors have improved the manuscript and complied to my remarks. The manuscript is now suitable for publication.
