Transport Properties of Strongly Correlated Fermi Systems

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors consider transport properties of heavy fermion metals and high Tc superconductor compounds. They propose a phenomenological explanation of observed temperature and magnetic field dependence assuming flat bands which seems to explain several experimental observations. However, the theoretical explanation in section 2 are not very sounded: The Landau Eq.(1) is only valid around for quasi-particles around the Fermi momentum, assuming a linear spectrum and isotropy. It is applied in Eq (3) and (4) outside it range of validty, without further justification. Despite that, the paper might provide some phenomenological characterisation of observed transport measurements in these systems. However, a proper judgement on it's validity is not possible within the review process.

Author Response

We thank the Reviewers for their reports and criticism that should make our paper better. We have accepted the criticism and added corresponding correction shown in green in the text.  

Reviewer  1 writes:

“The authors consider transport properties of heavy fermion metals and high Tc superconductor compounds. They propose a phenomenological explanation of observed temperature and magnetic field dependence assuming flat bands which seems to explain several experimental observations. However, the theoretical explanation in section 2 are not very sounded: The Landau Eq.(1) is only valid around for quasi-particles around the Fermi momentum, assuming a linear spectrum and isotropy. It is applied in Eq (3) and (4) outside it range of validty, without further justification. Despite that, the paper might provide some phenomenological characterisation of observed transport measurements in these systems. However, a proper judgement on it's validity is not possible within the review process.”

The Landau equation (1) is an exact, as it is shown in our papers (Ref. [8] and Density functional theory of fermion condensation, Phys. Lett. A 249, 237 (1998)). Thus, Eqs. (3) and (4) are not outside their range of validity. The corresponding explanations are added on pp. 2 and 3 and highlighted in green. We have also added Ref. [34]

 

 

 

Reviewer 2 Report

Comments and Suggestions for Authors

The review is interesting, relevant, and well-organized. The subject is very important in the context of current research in strongly correlated fermions. It gives a comprehensive and concise overview of the work done by the group of lead authors on the application of the fermionic condensation (FC) approach to heavy fermions and high-T_c cuprates. I can recommend the manuscript for publication with two suggestions for minor revisions:

1. In the Introduction the authors used the term "topological" for the fermionic condensation transition. I think the readership would benefit if the meaning of topological transition is explained in the present context.

2. In the discussion of the application of the phenomenological FC theory to the cuprates, the authors cite experimental papers , e.g. Refs 27, 28, 53, etc. On the other hand, in Ref. 53 another phenomenological theory, namely the  Marginal FLT (for a recent review, see e.g., Rev. Mod. Phys. 92 031001 (2020)) is applied to successfully explain linear conductivity and Planckian scaling observed. I think some comments in the manuscript are in order to make a comparative analysis of the two phenomenological approaches, and (presumably) to explain the advantages of the FC theory (if so).

 

 

 

Comments on the Quality of English Language

Minor corrections need to be done through the text

Author Response

We thank the Reviewers for their reports and criticism that should make our paper better. We have accepted the criticism and added corresponding correction shown in green in the text.  

Reviewer 2 wirtes:

 

“The review is interesting, relevant, and well-organized. The subject is very important in the context of current research in strongly correlated fermions. It gives a comprehensive and concise overview of the work done by the group of lead authors on the application of the fermionic condensation (FC) approach to heavy fermions and high-T_c cuprates. I can recommend the manuscript for publication with two suggestions for minor revisions:

1. In the Introduction the authors used the term "topological" for the fermionic condensation transition. I think the readership would benefit if the meaning of topological transition is explained in the present context.”

We have added the corresponding explanation on p. 2 highlighted in green.

Reviewer 2 wirtes:

“2. In the discussion of the application of the phenomenological FC theory to the cuprates, the authors cite experimental papers , e.g. Refs 27, 28, 53, etc. On the other hand, in Ref. 53 another phenomenological theory, namely the  Marginal FLT (for a recent review, see e.g., Rev. Mod. Phys. 92 031001 (2020)) is applied to successfully explain linear conductivity and Planckian scaling observed. I think some comments in the manuscript are in order to make a comparative analysis of the two phenomenological approaches, and (presumably) to explain the advantages of the FC theory (if so).”

We agree that the Marginal FLT gives good explanations to some experimental observations. Possibly the main difference between the Marginal FLT and FC theory is the account for the behavior of HF compounds in magnetic fields that make the system transit from the NFL behavior to the LFL one.  The corresponding explanations are added on pp.  4, 8, 11.