Functional Nanoscale Phase Separation and Intertwined Order in Quantum Complex Materials
Round 1
Reviewer 1 Report
Referee’s report on the paper
Functional nanoscale phase separation and intertwined order in quantum complex materials
by Gaetano Campi and Antonio Bianconi
The paper is a short review of authors' Scanning micro X-ray diffraction measurements, on two cuprates, La2-xSrxNiO4 and YBa2Cu3O6+y, with variable oxygen concentrations. It contains the presentation of data showing an interesting interplay at nanoscales between doped oxygen agglomerations and CDWs formed (presumably) within CuO2 planes, which is potentially an important element for the understanding of the influence of oxygen doping on phase diagrams of cuprates, and of the origin of high-Tc superconductivity phase particularly, stimulating for the further, both experimental and theoretical, investigations.
The paper is therefore recommended for publication in Special issue of Condensed Matter.
I also append few comments for authors’ considerations:
- As the review text it is rather short, but still sufficient to present the topic mentioned before. In my view, it would be advisable to avoid the tendency to cover the general relevance of high precision scanning X-ray method (2nd paragraph in the Introduction), including the list of various materials for which the method is relevant (and rather large number of corresponding cited references) (1st paragraph in the Introduction), as well as general statements on possible use of the method (last paragraph in the section “Discussion”.
- Instead, more details regarding the data on two cuprates and their interpretation (in particular one could make the paragraph between the lines 109-115) more redable), and particularly some hints on their relevance for the mechanism of ordered phases appearing in corresponding phase diagrams, could be helpful for readers mainly interested in high Tc
Technical remarks:
- 1c: Aside from the hysteretic effect (which is by itself intriguing), it is not clear whether the flux dependence of the intensity is a simple proportionality (larger flux intensity – larger scattering intensity), or there is some more essential content. In other words, is something hidden behind “arbitrary units” at the intensity axis?
- Line 68: acronym QM not introduced before?
- Line 112 and elsewhere: what is the scale of the cut off x0. E.g. what is meant by saying that x0 is less than ten, etc?
- Could the sentence in lines 182-3 be made more legible?
Author Response
REFEREE 1
The paper is a short review of authors' Scanning micro X-ray diffraction measurements, on two cuprates, La2-xSrxNiO4 and YBa2Cu3O6+y, with variable oxygen concentrations. It contains the presentation of data showing an interesting interplay at nanoscales between doped oxygen agglomerations and CDWs formed (presumably) within CuO2 planes, which is potentially an important element for the understanding of the influence of oxygen doping on phase diagrams of cuprates, and of the origin of high-Tc superconductivity phase particularly, stimulating for the further, both experimental and theoretical, investigations.
The paper is therefore recommended for publication in Special issue of Condensed Matter.
I also append few comments for authors’ considerations:
As the review text it is rather short, but still sufficient to present the topic mentioned before. In my view, it would be advisable to avoid the tendency to cover the general relevance of high precision scanning X-ray method (2nd paragraph in the Introduction), including the list of various materials for which the method is relevant (and rather large number of corresponding cited references) (1st paragraph in the Introduction), as well as general statements on possible use of the method (last paragraph in the section “Discussion”).
Reply. We have changed the introduction (lines 44-61 of the revised manuscript), as requested.
Instead, more details regarding the data on two cuprates and their interpretation (in particular one could make the paragraph between the lines 109-115) more readable), and particularly some hints on their relevance for the mechanism of ordered phases appearing in corresponding phase diagrams, could be helpful for readers mainly interested in high Tc.
Reply. We have revised the paragraph (lines 107-114 in the revised manuscript) taking into account this comment.
Technical remarks:
1c: Aside from the hysteretic effect (which is by itself intriguing), it is not clear whether the flux dependence of the intensity is a simple proportionality (larger flux intensity – larger scattering intensity), or there is some more essential content. In other words, is something hidden behind “arbitrary units” at the intensity axis?
Reply. The X ray illumination procedure, described in the added ref. 74, has been specified in lines 82-91 of the revised manuscript. The low flux and high flux correspond to 0.5 1014 photons s-1 cm-2 and 5.0 1014 photons s-1 cm-2. The temperature change rate has been of 1K min-1 in both low flux and high flux illumination.
Line 68: acronym QM not introduced before?
Reply. We have replaced the acronym QM with quantum materials, in the whole manuscript.
Line 112 and elsewhere: what is the scale of the cut off x0. E.g. what is meant by saying that x0 is less than ten, etc?
Reply. We have clarified the meaning of the cut-off, x0, in the exponentially truncated power law used as model for the intensity maps in Fig. 2, as discussed in ref. 38. We changed the text (lines 107-114 of revised manuscript) and the caption of Fig. 2.
Could the sentence in lines 182-3 be made more legible?
Reply. The sentence has been changed, taking into account also the suggestions of referee 3.
Reviewer 2 Report
Condensed Matter 1442179
Functional nanoscale phase separation and intertwined order in quantum complex materials
By Gaetano Campi and Antonio Bianconi
The manuscript by Campi and Bianconi reviews micro synchrotron xray scanning investigations on the two high-Tc superconductors La2CuO4+y and HgBa2CuO4+y. These investigations gave evidence for structural (and electronic, as the authors concede in their Discussion paragraph) inhomogeneity expressed in separate (mutually avoiding) regions in the crystals. It appears that most of the results reported in the manuscript have been published in the past decade, partially in high-ranked journals. A review of these results is timely and useful for the community
A general hesitation with the reasoning in the manuscript is related to the statement put prominently in the 2nd paragraph of the Introduction namely that ‘multiscale lattice disorder …. overcame the belief that assigned quantum functionality to electronic phase separation with intertwined orders ….’ It is one of the challenging scientific problems of high-Tc superconductivity (born out from antiferromagnets) that the phonon, the electronic and magnetic subsystems are intimately connected. In my view, lattice disorder necessarily implies electronic and magnetic inhomogeneity. This aspect should be discussed and acknowledged in the Discussion paragraph.
With respect to the style the manuscript I have a more general problem: The manuscript is announced as a ‘Review’ article which, in fact, it appears to be. Meanwhile while reading the text in more detail I was under the impression that original and probably new scientific results are simultaneously reported, however these are not immediately distinguishable from each other. For example, references to previous works are given in the text but there are no explicit sources quoted for the figures.
My misconception that published and (possibly) new results are simultaneously reported arises also since the final paragraph on ‘Materials and Methods’ somehow implies that original and new data are contained in a manuscript. Otherwise, in a Review style article reference to materials and experimental methods could have been easily be made by quoting already published results.
Checking some of the references, I found that quite a number of figures have already been published, for example for La2CuO4+y in Nature Letters, Vol 466 from 2010, HgBa2CuO4+y in Nature Letters 522 from 2015. However, reproduction of figures one-to-one (as e.g. in case of fig. 2 in the manuscript) clearly requires an annotation or reference (e.g. in the captions) from where these figures have been copied from. Otherwise Copyright issues may be readily encountered.
I also recommend that the figure captions should be more explicit and detailed. For example, non of them names the compound the presented data are related to.
In summary, before the manuscript can be accepted for publication deserves a revision in order to clearly say what has already been published and whether there are new results. In addition, I feel it would be extremely helpful for the interested reader to amend the figure captions to make them more ‘self-contained’.
Author Response
REFEREE 2
The manuscript by Campi and Bianconi reviews micro synchrotron x ray scanning investigations on the two high-Tc superconductors La2CuO4+y and HgBa2CuO4+y. These investigations gave evidence for structural (and electronic, as the authors concede in their Discussion paragraph) inhomogeneity expressed in separate (mutually avoiding) regions in the crystals. It appears that most of the results reported in the manuscript have been published in the past decade, partially in high-ranked journals. A review of these results is timely and useful for the community.
A general hesitation with the reasoning in the manuscript is related to the statement put prominently in the 2nd paragraph of the Introduction namely that ‘multiscale lattice disorder …. overcame the belief that assigned quantum functionality to electronic phase separation with intertwined orders ….’ It is one of the challenging scientific problems of high-Tc superconductivity (born out from antiferromagnets) that the phonon, the electronic and magnetic subsystems are intimately connected. In my view, lattice disorder necessarily implies electronic and magnetic inhomogeneity. This aspect should be discussed and acknowledged in the Discussion paragraph.
Reply. We thank the referee for this important comment. In fact, while in the literature is very common to speak about electronic phase separation in High Tc superconductors (electronic and magnetic inhomogeneity), the main experimental result of Scanning X ray Diffraction is that the “lattice disorder necessarily implies electronic and magnetic inhomogeneity.” This concept has been clarified in the revised manuscript (lines 47-61).
With respect to the style the manuscript I have a more general problem: The manuscript is announced as a ‘Review’ article which, in fact, it appears to be. Meanwhile while reading the text in more detail I was under the impression that original and probably new scientific results are simultaneously reported, however these are not immediately distinguishable from each other. For example, references to previous works are given in the text but there are no explicit sources quoted for the figures.
My misconception that published and (possibly) new results are simultaneously reported arises also since the final paragraph on ‘Materials and Methods’ somehow implies that original and new data are contained in a manuscript. Otherwise, in a Review style article reference to materials and experimental methods could have been easily be made by quoting already published results.
Checking some of the references, I found that quite a number of figures have already been published, for example for La2CuO4+y in Nature Letters, Vol 466 from 2010, HgBa2CuO4+y in Nature Letters 522 from 2015. However, reproduction of figures one-to-one (as e.g. in case of fig. 2 in the manuscript) clearly requires an annotation or reference (e.g. in the captions) from where these figures have been copied from. Otherwise Copyright issues may be readily encountered.
Reply. We thank the referee for this comment that give us the possibility to clarify this point. In this review we do not show new results. We agree that a review of our results can be useful for the community; furthermore, over time new discoveries and general cultural evolution can offer new points of view. In this context, e.g. we have highlighted the interfaces between separate regions in the crystals giving the phase separation already investigated in previous works. Thus, we do not show any new data, but we have placed the figures and the results in an enriched perspective. This should allow us to not encounter the Copyright issues. For this purpose, we have also modified Fig. 2 and Fig.4 with maps and plots slightly different from those in our original work (ref. 38 and ref. 7).
I also recommend that the figure captions should be more explicit and detailed. For example, none of them names the compound the presented data are related to.
Reply. We have revised all captions, making them more explicit and detailed.
In summary, before the manuscript can be accepted for publication deserves a revision in order to clearly say what has already been published and whether there are new results. In addition, I feel it would be extremely helpful for the interested reader to amend the figure captions to make them more ‘self-contained’.
Reply. We have revised the text and the figure captions taking into account this comment.
Reviewer 3 Report
Just some comments and questions to the authors:
- I think, the functionality of the investigated materials may be extended in the direction of information storage. I would like to ask the authors to answer (may be , to comment in the article, in “Discussion”) – if is it possible to use this materials for record and storage information, using the X ray photo illumination ( panels (b) and (c), fig.1)).
2) formation of metallic and insulating domains with oxygen-rich (O-i) and oxygen-poor regions (CDW), a strongly anticorrelated in the space, as shown in the fig3a. leads to topologic configuration similar to two-dimensional fractals of the “Sierpinsky gasket” type (see, for example, in: A.S. Sidorenko. Fractal geometry in superconductivity. Moldavian Journal of the Physical Sciences; ISSN 1810-648X; ; v. 1(4); p. 102-105 on-line: https://inis.iaea.org/search/search.aspx?orig_q=RN:42087566 ). More, spatial anticorrelated the O-i rich and CDW rich regions, looks like two Sierpinsky gaskets inserted one into the other - as reflected in a mirror. One more evidence of appearance of the fractal geometry in the investigated samples serves the exponential decay of the probability density function dependence on the domains size – this dependence propagates more than two orders of magnitude along the size coordinate, confirming the existence of the hierarchy of domains sizes. In ceramic high-Tc superconductors such hierarchy of the grains size leads to temporary fractality – long-term relaxation of the remanent magnetization ( GABOVICH, A.M.; MOISEEV, D.P.; PANAITOV, G.I.; SIDORENKO, A.S.; POSTNIKOV, V.M. Relaxation of the magnetization in superconducting oxides. Modern Phys. Lett. B. 1989, 3(10), 1503-1509).
3) Question: does the authors investigated magnetization of their samples? It should demonstrate similar fractal behavior, due to existence of hierarchy of superconducting domains sizes.
Comments for author File: 
Comments.pdf
Author Response
REFEREE 3
I think, the functionality of the investigated materials may be extended in the direction of information storage. I would like to ask the authors to answer (may be, to comment in the article, in “Discussion”) – if is it possible to use these materials for record and storage information, using the X ray photo illumination (panels (b) and (c), fig.1)).
Reply. We thank the referee for this hint and we have considered it in the discussion (lines 196-198 of revised manuscript).
2) formation of metallic and insulating domains with oxygen-rich (O-i) and oxygen-poor regions (CDW), a strongly anticorrelated in the space, as shown in the fig3a, leads to topologic configuration similar to two-dimensional fractals of the “Sierpinsky gasket” type (see, for example, in: A.S. Sidorenko. Fractal geometry in superconductivity. Moldavian Journal of the Physical Sciences; ISSN 1810-648X; v. 1(4); p. 102-105 on-line: https://inis.iaea.org/search/search.aspx?orig_q=RN:42087566). More, spatial anticorrelated the O-i rich and CDW rich regions, looks like two Sierpinsky gaskets inserted one into the other - as reflected in a mirror. One more evidence of appearance of the fractal geometry in the investigated samples serves the exponential decay of the probability density function dependence on the domains size – this dependence propagates more than two orders of magnitude along the size coordinate, confirming the existence of the hierarchy of domains sizes. In ceramic high-Tc superconductors such hierarchy of the grains size leads to temporary fractality – long-term relaxation of the remanent magnetization (GABOVICH, A.M.; MOISEEV, D.P.; PANAITOV, G.I.; SIDORENKO, A.S.; POSTNIKOV, V.M. Relaxation of the magnetization in superconducting oxides. Modern Phys. Lett. B. 1989, 3(10), 1503-1509).
Reply. We appreciate this comment and we have placed it in the discussion (lines 196-198 of revised manuscript), adding the suggested references [76], [77].
3) Question: does the authors investigated magnetization of their samples? It should demonstrate similar fractal behavior, due to existence of hierarchy of superconducting domains sizes.
Reply. We have focused our crystallographic research. The material growth groups have characterized the magnetization of our samples.
Round 2
Reviewer 1 Report
I have passed through the author' response and the revisions in the manuscript. Since they have met the remarks and suggestions from referees' reports (including mine), the manuscript is in my opinion now fully acceptable for publication.
Reviewer 2 Report
Condensed Matter 1442179-1st revision
Functional nanoscale phase separation and intertwined order in quantum complex materials
By Gaetano Campi and Antonio Bianconi
The authors have amended and noticeably improved the manuscript. My irritation as to what are new results and what has already been described before in other publications is largely mitigated by the revised version. Also the discussion is now less exclusively focused on the structural aspects of phase separation.
Even though the sources of the shown figures are referenced copyright issues may still be an issue.
In summary, the revised manuscript is concise, reviews interesting results is well written interesting and useful. I recommend accepting the manuscript for publication.
A I notices a very few spelling mishaps that need to be corrected.
