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diff --git a/referee_comments.txt b/referee_comments.txt new file mode 100644 index 0000000..6bf1273 --- /dev/null +++ b/referee_comments.txt @@ -0,0 +1,145 @@ +> Re: BN13654 +> Elastic properties of hidden order in URu 2Si 2 are reproduced by a +> staggered nematic +> by Jaron Kent-Dobias, Michael Matty, and B. J. Ramshaw +> +> Dear Jaron Kent-Dobias, +> +> The above manuscript has been reviewed by two of our referees. +> Comments from the reports appear below. +> +> These comments suggest that the present manuscript is not suitable for +> publication in the Physical Review. +> +> Yours sincerely, +> +> Sarma Kancharla +> Associate Editor +> Physical Review B +> Email: prb@aps.org +> https://journals.aps.org/prb/ +> +> NEWS FROM THE PHYSICAL REVIEW JOURNALS +> +> Announcing a new Physical Review journal: PRX Quantum +> https://go.aps.org/2Q0uVwP +> +> Celebrating 50 years of Physical Review A, B, C, and D +> https://go.aps.org/2IDjVBM +> +> APS is offering promotional open access fee discounts on most +> journals in 2020 +> https://go.aps.org/3388lYG +> +> ---------------------------------------------------------------------- +> Report of the First Referee -- BN13654/Kent-Dobias +> ---------------------------------------------------------------------- +> +> The work deals with a purely phenomenological model for the “hidden” +> order parameter if URu2Si2, with particular emphasis on the expected +> elastic properties. The work might eventually be suitable for Phys. +> Rev. B, but some aspects are not clear to me. +> +> The main result is Fig. 2, where the behavior around TN is difficult +> to see. I suggest to add zooms on that crucial T-range, where it seems +> to me that there is a qualitative difference between model and +> experiments. The justification given by the Authors (“mean field +> theory—which is based on a small-eta expansion—will not work +> quantitatively far below the transition where eta has a large nonzero +> value and higher powers in the free energy become important”) does not +> look plausible as the disagreement does not appear to develop slowly +> as T decreases, but appears immediately below TN, where eta is small. + +The disagreement between the theory at low temperature is resolved by the +addition of an additional interaction in the mean-field free energy of the form +ε²η², now shown in Fig. 2 as a thin black line. + +> Is it not clear how discriminatory is the agreement above TN in 2a, 2b +> and 2c. Are calculation results robust over a wide range of fitting +> parameters, or does the agreement result from a fine-tuning? (e.g., +> the presence of a maximum at 120 K in 2b). + +[Not exactly sure what this means.] + +> Is it possible to say something about the c/a ratio, which displays a +> non-trivial T-dependence? + +[Not sure what this means either. Is this asking about the ratio of lattice constants?] + +> At last, I understand that the model is meant to be purely +> phenomenological, but given the plethora of publications on URu2Si2 +> over 30 years, where any conceivable order parameter has been proposed +> as candidate, the Authors should make a connection between their +> abstract OP and possible physical realizations. For instance, in the +> simplest framework of localized f-electrons, what ionic moments would +> fit the present proposal? + +[Mike, can you help with this?] + +> ---------------------------------------------------------------------- +> Report of the Second Referee -- BN13654/Kent-Dobias +> ---------------------------------------------------------------------- +> +> In this paper, possible elastic properties of URu2Si2 are studied with +> focusing on the long-standing hidden order (HO) problem. The authors +> introduce a generic form of the free energy density for the elastic +> energy, a modulated order parameter, and their mutual coupling, and +> analyze the temperature dependences of the elastic constants by +> minimizing the free energy. It is shown that the B1g component +> exhibits a remarkable softening with decreasing temperature and a cusp +> singularity at the HO transition point, and these results are compared +> with recent ultrasound experiments. From the comparison, the authors +> conclude that the HO phase of URu2Si2 originates from the modulated +> B1g order parameter. +> +> In the course of evaluation, the referee does not recommend the paper +> to be published in PRB, mainly based on the following reason. +> +> 1) The scheme for the coupled strains in this paper is quite standard +> within the mean-field treatment and does not provide a novel +> theoretical advance. +> +> 2) One can generically expect several sources for softening elastic +> constants. For example, the authors in ref.25 also succeeded in the +> quantitative fits in the framework of a 4f crystal field model for T > +> T_HO. Thus, the fitting is not regarded as the decisive evidence on +> the validity of the model. + +[Not sure how to respond to this; Brad?] + +> 3) The agreement of C[B1g] in the region T<T_HO is poor, though only +> the cusp at T_HO seems qualitatively consistent with the experiment. +> Moreover, the referee expects that even a cusp structure in the +> elastic constants is not unique to this model; it can be obtained from +> more general models beyond the linear coupling (4), within the +> mean-field level. Therefore, the referee thinks that this analysis +> does not lead uniquely to the authors' arguments on the realization of +> the B1g order parameter. + +The disagreement between the theory at low temperature is resolved by the +addition of an additional interaction in the mean-field free energy of the form +ε²η², now shown in Fig. 2 as a thin black line. + +While terms like this provide cusp-like features in the modulus for each strain +symmetry, they cannot explain the 1/ΔT softening seen in the high-temperature +phase, since their contribution to the response function is zero above T_c. + +> 4) The most important point in the HO problem is the microscopic +> identification of symmetry breaking and the order parameter. In spite +> of the long history in research over almost 40 years, there is no +> experimental evidence of the formation of any superlattice structure +> at least at ambient pressure. So, the proposed modulated order is not +> consistent with the absence or identification of symmetry breaking. +> The authors do not provide any resolution on that point which is the +> most relevant in this problem. + +The articles below provide experimental evidence for the formation of +superlattice structure along the c-axis at ambient pressure. + +[I pulled these from our citation on the estimate for q_*. Do they actually provide the evidence we need?] + +https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.111.127002 +https://journals.aps.org/prb/abstract/10.1103/PhysRevB.43.12809 +https://journals.jps.jp/doi/10.1143/JPSJ.79.064719 +https://www.nature.com/articles/nphys522 + |