Radiation Problems Accompanying Carrier Production by an Electric Field in the Graphene
, Dmitry M. Gitman 1,3,4, Vadim V. Dmitriev 5, Anatolii D. Panferov 5 and Stanislav A. Smolyansky 1,5,*Round 1
Reviewer 1 Report
The authors work in the kinetic approach to describe the quasiparticle-pair creation effects in the graphene. The theoretical results of the paper have a strong potential to be verified experimentally which gives a particular value to the manuscript. While most of the derivations are well-justified, I have a few (all optional) comments that could be considered by the authors for possible implementation in the revised version of the manuscript.
— It is unclear to get the cos-factor in (25) for the phase (26). Surely, it could be there but one needs exp-factors that should be present in the field operators but not indicated explicitly in the manuscript. Can the authors clarify this point?
— The paragraph in between Eqs. (42) and (43), various comments:
- In fact, the real graphene interacts with the A3 component because the real graphene sheet is always corrugated. It is seen in the image of the book cover by M.I. Katsnelson "Graphene: Carbon in Two Dimensions" and discussed in Ref.[33]. The real graphene is never flat. Let's think in the following that the authors consider an academic limit of the flat graphene, which is a good approximation in the low-energy regime anyway.
- Condition (43) implies that the authors assume that there are no electromagnetic losses due to electromagnetic radiation in off-plane directions. It is a somewhat artificial restriction. Moreover, the first relation in equation (43) selects a very narrow band in the photon phase space. I understand that the authors want to "close" the system, but it would be nice to estimate the consequences of this restriction crude to the relevance of the discussed effects to the real graphene.
- Excluding 3d photons and working with a 2d physics may lead to potentially wrong results, please see below.
— For the electronic properties of graphene, the electromagnetic interaction is essentially instantaneous (the velocity of light may be taken infinite: the bulk 3d photons lead to instantaneous interaction). The long-range interactions are well described by the non-local instantaneous Hamiltonian in Eq. (102) of the same review [33]. This form of this Hamiltonian -- which proved to successfully describe the most IR properties of graphene -- is shaped by the 3d exchanges of photons which were neglected in the manuscript. While this comment does not require an explicit answer now, but it may probably be taken into account in the future development of this work.
— I suggest to use the "int" subscript for the interaction Hamiltonian (47) and below since there is the same abbreviation "in" in the in-states at the beginning of the article.
— Do the authors fix a gauge? The physical mass gap in (73) does not look gauge-invariant [although for the particular form of the wave it gets a gauge-invariant form (74)].
— Providing the value of mass in electron-volts may be a dangerous practice. The effective mass gap m* quoted in line number 336 is huge: given that 1eV =1.2 ×104 Kelvin, the reader would "see" the effective temperature in 100 million Kelvins (!). However, it's the energy and not mass that is relevant for cond.mat., applications. And the energy is much smaller given the smallness of the Fermi velocity. Let's calculate: the energy (73) at rest (p=0) is equal to ?= m* vF2. Given the value of the Fermi velocity (in the footnote on page 5), we get the following energy for the first experimental study:
? = 1.5 × 104 (vF/c)2 eV = 160 meV = 1800 K,
which is a bearable quantity. I suggest presenting the mass in me, while also calculate the energy corresponding to the mass gap in eV.
Finally, the manuscript contains a certain number of typos so that I suggest to re-read it carefully. I spotted the following misprints (with the line or equation number shown first):
162: consider → considers, carries → carriers
165: does not → do not
178: finding → in order to find
Eq.(16): remove "_" in the commutator?
204: anomalous means → the following anomalous expectation values (?)
291 and below: "eh" in italic? (not essential, but many authors use italic). Please also insert "eh" in the abbreviation section at the end of the article;
375: describes → describe.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
In this article studied a number of physical processes occurring in a flat one-dimensional graphene structure 2 under the action of strong time-dependent electric fields. This problem is relevant for modern physics. The research results are reliable, well presented, and of undoubted interest. I believe that this article can be published in the journal Universe.
Author Response
We are thankful to the referee's comment!
