Peer review of: Switching of band inversion and topological surface states by charge density wave (2020)


RR2

REVIEWERS' COMMENTS:
Reviewer #1 (Remarks to the Author):
  I have reviewed in detail the resubmitted manuscript, the reports of the other two reviewers, and the
 authors' responses to the reviewers' comments. The authors have made a genuine effort in clarifying
 in detail all the issues raised in those reports. They have significantly and extensively improved the
 manuscript by adding or updating figures, appropriately adding additional supplemental material, as
 well as by providing additional experimental details and discussion in the main text. It is now clear
 which results and conclusions are solid, and the limitations in addressing some of the outstanding
 questions (such as the DFT calculations for the ground-state of the 1T' phase, whose numerical
 difficulties I now better appreciate and understand).
 With these changes, the overall set of results here has become even more compelling. The manuscript
 is now suitable for publication.
 Reviewer #2 (Remarks to the Author):
 The revised manuscript by Mitsuishi et al. maintains the high quality of data and analysis, and clarifies
 all the points raised in my review. I do think the paper in this form deserves publication in Nature
 Communications , with some minor modifications (see below)
 In particular, the discussion of the accuracy of calculation, the clarification on the selective change of
 Dirac bands, and the unclear point regarding the composition vs. temperature of the transition have
 been clearly addressed in the present revised version. Accordingly, changes in the main text, figures
 and supplementary have been included.
 I think that, still, two minor points should be addressed prior publication:
 a) regarding fig. R6 (S2c), authors should include, either in the text or in figure caption, their phrase
 regarding the highly warped Fermi surfaces (end of point 3 in their reply on page.12), this will further
 clarify their results
 b) authors may consider to sligthly modify Figure 5 panel i). In fact, being panel i) extracted from h),
 and being the difference very small (as clearly seen in the corresponding figure in the supplementary),
 I would suggest to select e.g. only the 0.2 eV to -0.2 eV section to highlight the presence of a
 difference.
 Reviewer #3 (Remarks to the Author):
 I have reviewed the response by Mitsuishi et al. It is clear that the authors have invested a significant
 amount of effort to address my concerns, as well as those of the other reviewers. The authors have
 addressed or responded to my concerns regarding the presentation of their data, including the
 addition of spin-resolved results, the doping levels, and organization of the manuscript.
 However, the remaining concern of mine is the most important one, and is also echoed in the
 comments of Reviewer #2 ("...the presented interpretation is not conclusive in that sense...as the
 topology of a material is a property of the system as a whole, the data seems to demonstrate that the
 topology is conserved across the CDW transition...this is "the" focal point/question of the paper and
 needs to be addressed more convincingly").
 
Unfortunately, it appears that (despite the authors' efforts) the DFT calculations are not able to
 answer this question conclusively, presumably due to the complex crystal structure. The authors make
 some arguments which are plausible, but not concrete. Without a clear resolution of this issue, which
 (in my opinion) is the key result of this paper, I am still reluctant to recommend this manuscript for
 publication.