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Detect Axial Gauge Fields with a Calorimeter

by Matteo Baggioli, Maxim N. Chernodub , Karl Landsteiner, Maria A. H.Vozmediano

Submission summary

As Contributors: matteo Baggioli · Karl Landsteiner · Maria Vozmediano
Preprint link: scipost_202007_00054v1
Date submitted: 2020-07-11 02:00
Submitted by: Baggioli, matteo
Submitted to: SciPost Physics Core
Discipline: Physics
Subject area: Condensed Matter Physics - Theory
Approach: Theoretical

Abstract

Torsional strain in Weyl semimetals excites a unidirectional chiral density wave propagating in the direction of the torsional vector. This gapless excitation, named the chiral sound wave, is generated by a particular realization of the axial anomaly via the triple-axial (AAA) anomalous diagram. We show that the presence of the torsion-generated chiral sound leads to a linear behavior of the specific heat of a Weyl semimetal and to an enhancement of the thermal conductivty at experimentally accessible temperatures. We also demonstrate that such an elastic twist lowers the temperature of the sample, thus generating a new, anomalous type of elasto-calorific effect. Measurements of these thermodynamical effects will provide experimental verification of the exotic triple-axial anomaly as well as the reality of the elastic pseudomagnetic fields in Weyl semimetals.

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Submission scipost_202007_00054v1 on 11 July 2020

Reports on this Submission

Anonymous Report 1 on 2020-9-7 Invited Report

Report

This manuscript is a follow-up of the paper M. N. Chernodub and M. A. H. Vozmediano, Chiral sound waves in strained Weyl semimetals, Phys. Rev. Research1, 032040 (2019), by two of the authors (Chernodub and Vozmediano) of that paper, which is cited as reference 22 in the current manuscript. Given its follow-up nature, it is a somewhat difficult decision on whether or not to recommend it for publication on SciPost Physics Core. There is some material used in this manuscript [for instance, Eq. (17)] whose derivation is given in Ref. 22. This is perhaps the only part that is not really self-contained in the text. Otherwise I would say that the manuscript is well suited for a broad audience of physicists. However, this seems to not be a relevant criterion for SciPost Physics Core, so let me be more precise here.

The manuscript is making simple and interesting predictions for experimentally detecting so called axial gauge fields within a condensed matter context where Weyl semi-metals are used. The origin of the effects predicted in the manuscript is related to a so called chiral sound wave (CSW), which arises due to strain in the sample, making the separation between the Weyl nodes dependent on spacetime. In my view this is by itself of great originality. The thermal effects predicted are generally explained pedagogically, so this is definitely readable by experimentalists, which I would say is a plus point. Also related to the usefulness to this target audience, there is a detailed section (Sect. 4) dicussing the experimental accessibility. Here is unfortunate that Eq. (17) is derived in Ref. 22, something I mentioned briefly above. I would recommend the authors to give some additional motivation for Eq. (17), since this is one section that is particularly important for experimentalists. One possibility would be to include a short appendix recalling in simple terms (if possible) the derivation made in Ref. 22.

Another thing that would need improvement is the discussion of the thermal conductivity in section 5. In that section Eq. (24) is mentioned as a "general expression", something that is certainly not true. Eq. (24) is valid in the dilute limit. A similar formula, also valid in the dilute limit, can be derived for the viscosity (is it not relevant here?). I would recommend the authors to clearly state the regime of validity of Eq. (24).

Given the interesting physics involved, describing a condensed matter incarnation of concepts originating from high-energy physics, and the fact that the main purpose of this manuscript is to propose a way to access experimentally the effect of an exial gauge field, I believe that it is a significant work that may lead to important experimental results in the field. Therefore, after the minor considerations above have been addressed, I would recommend to publish this manuscript in SciPost Core.

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