Topological Phase Diagram of BiTeX–Graphene Hybrid Structures

Round 1

Reviewer 1 Report

Topological phase diagram of BiTeX graphene hybrid structures: applsci-615003

The authors have responded to all issues raised and have submitted a reorganized, extended version of their manuscript. All crucial issues have been corrected. Format and style have been adjusted to the journal's standard. Details regarding the treatment of spin-orbit coupling and the choice of the DFT functional are now provided. The article now mentions explicitly where it goes beyond closely related previous research. The corresponding phase diagrams of BiTeCl-graphene and BiTeI-graphene systems and their discussion have been added to the manuscript. Citations have been added for the sake of completeness, and the computational approach is presented in greater detail, more independent of previous publications, which improves the overall readability. Therefore, I can now recommend a publication of this work in MDPI Applied Sciences. Two typos/suggestions are given below.

line 46: I suggest the following rearrangement of the sentence: "In this manuscript we investigate in detail the phase diagrams of the BiTeCl-graphene and BiTeI-graphene systems as obtained from density functional theory calculations and compare them to the BiTeBr–graphene system."

line 141: "These systems lead"

 

 

Reviewer 2 Report

BiTeBr-graphene, BiTeCl-graphene, and BiTeCl-graphene are in the same class and have the same structure. Of course they have similar phase diagrams. All of them have been studied in Nanoscale, 11, 12704 (2019). Although only one representative phase diagram for BiTeBr-graphene was showed in Fig.4, the authors mentioned in the paper that 

"We only present results for BiTeBr further calculations show that BiTeCl behaves qualitatively in the same fashion. BiTeI turns metallic instead of a trivial insulator due to some non graphene bands reaching the Fermi level as pressure is increased."

The conclusion of this manuscript is also above content. In principle, this manuscript is just a repetition of above paper. According to the guidelines for reviewers, the paper is not original, the result is not significant, and is therefore not interesting for the readership of the Journal. Based on above reasons, I do not recommend the manuscript for publication in Applied Sciences.  

 

 

    

Reviewer 3 Report

The changes in the paper are satisfactory. I recommend the publication of this paper. 

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

Topological phase diagram of BiTeX graphene hybrid structures: applsci-600737

The authors investigate the topological phase diagrams of bismuth tellurohalide graphene by periodic density functional theory. It is reported that uniaxial, in-plane tensile strain gives rise to a non-trivial band gap at an experimentally reasonable compression, making this material potentially interesting for quantum technologies. Phase diagrams are provided for three systems.

This article is an interesting continuation of the group's work on graphene hybrid structures. However, it is obviously written in letter style and has not even been adjusted to the journal's typical style, which includes standard separations such as introduction, results, methods and conclusions. In the submitted version all of the text appears as "introduction". As a consequence, it is unnecessary compact and lacks important details in several paragraphs. On the first page, the authors claim to provide a "detailed description" of this system, but fail to deliver. Therefore, this article can not be recommended for publication in its current form. Also, an article which is so closely related to previous work should emphasize where it goes beyond that previous research; a phase diagram, at least for BiTeBr, has already been provided in Ref. 22. A few points of critics and further suggestions are mentioned below.

Besides these more technical issues, the article lacks a clear linking of the introductive comments on spin-orbit coupling in these materials to the actual DFT calculations in the later part. How did the authors address spin orbit coupling within the SIESTA package? How trustworthy is this treatment, and which value can be used as a reference to for comparison to the experiment? Even more advanced, high-level treatments of open-shell systems (e.g. multi-reference methods) might have problems with retrieving the full amount of spin-orbit coupling. This should be addressed in an updated, extended version of this manuscript. This follow-up article could e.g. be used to explain relations between the SO parameters appearing in the effective Hamiltonian (Equation 4 in Ref 22) and the computational simulation of the system. None of this can be found in the current manuscript.

Regarding the DFT calculations themselves, no explanation is given to why the PBE functional has been chosen. Parameter choices (thresholds, etc.) seem reasonable, but the justification of the authors is based on computation of bulk BiTeI, which gives little information on the actual performance of the hybrid compound including graphene. An explanation or comment should be given.

In the conclusions, the authors include comments on thermochemistry, which do not seem to be backed up by the actual calculations. The meaning of "band gap amplitudes way above room temperature" remains unclear.

Typos and minor issues

Please also see the list of minimal corrections/suggestions given below. 

p. 3, left col.: "enhances"

p. 3, left col.: "SOC can be introduced to graphene by van der Waals constituents ..."

p. 3, right col.: "we give a detailed theoretical description of these systems based on density functional theory."

(It is questionable if DFT should be called an "ab initio" technique; but this is just a comment)

p. 4, left col.: Computational results are mentioned before the actual technique/approach/level of theory is discussed.

p. 4, left col.: "may alter"

p. 4, left col.: "not let the atomic positions relax"

Citation 22 is incomplete; please add a full reference to the publication in Nanoscale.

Reviewer 2 Report

In this manuscript the authors show that the topological phase can be realized in the heterostructures of graphene and BiTeX (X=I,Br,Cl) under the effect of uniaxial in-plane tensile and out-of plane compressive strain.

Generally speaking, there is nothing new in terms of both idea and technical aspects. All the results have been published in Nanoscale, 11, 12704 (2019) by the same authors.

I, therefore, do not recommend this manuscript for publication in Applied Sciences.

Reviewer 3 Report

The paper investigating on the topological phase diagrams of bismuth tellurohalide/graphene heterostructures by means of first principles calculations is very interesting.

However, the manuscript as downloaded does not have reference numbers in the text, only question marks (see the file attached). Also the numbers of the Figures are missing in the text. This needs to be fixed.

Further, I would suggest to better elaborate on the phase diagram discussion (Fig 2), deepening the discussion in the text.

Comments for author File: Comments.pdf