# Novel attractive pairing interaction in strongly correlated superconductors

### Submission summary

 As Contributors: Tanmoy Das Arxiv Link: https://arxiv.org/abs/1906.01312v2 Date accepted: 2019-11-11 Date submitted: 2019-09-30 Submitted by: Das, Tanmoy Submitted to: SciPost Physics Discipline: Physics Subject area: Condensed Matter Physics - Theory Approach: Theoretical

### Abstract

Conventional and unconventional superconductivity, respectively, arise from attractive (electron-phonon) and repulsive (many-body Coulomb) interactions with fixed-sign and sign-reversal pairing symmetries. Although heavy-fermions, cuprates, and pnictides are widely believed to be unconventional superconductors, recent evidence in one of the heavy fermion superconductor (CeCu$_2$Si$_2$) indicate the presence of a novel conventional type pairing symmetry beyond the electron-phonon coupling. We present a new mechanism of attractive potential between electrons, mediated by emergent boson fields (vacuum or holon) in the strongly correlated mixed valence compounds. In the strong coupling limit, localized electron sites are protected from double occupancy, which results in an emergent holon gauge fields. The holon states can, however, attract conduction electrons through valence fluctuation channel, and the resulting doubly occupied states with local and conduction electrons condense as Cooper pairs with onsite, fixed-sign, $s$ -wave pairing symmetry. We develop the corresponding self-consistent theory of superconductivity, and compare the results with experiments. Our theory provides a new mechanism of superconductivity whose applicability extends to the wider class of intermetallic/mixed-valence materials and other flat-band metals.

### Ontology / Topics

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Published as SciPost Phys. 7, 078 (2019)

We have uploaded our responses in pdf file to both referees' reports. Our response files also included our revised manuscript with blue color text highlighting the revisions made here. The same version without the blue color is also uploaded on arxiv (arXiv:1906.01312v2). Since our responses include equations and figures, we are not able to type it on this box.

### List of changes

1) We have expanded the Discussion section (last section below bibliography)
2) We have added new citations in Ref. 31, 32, 52.
3) Few typographical errors are rectified.
4) In several places, few comments are added and/or revised in accordance to referees' suggestions.

(All changes are highlighted in blue color in the revised pdf file appended to each referee reports.)

### Submission & Refereeing History

Resubmission 1906.01312v2 on 30 September 2019
Submission 1906.01312v1 on 6 June 2019

## Reports on this Submission

### Report

In the revised manuscript, the authors made some improvement. In my view, the author's response to the referee reports and the changes in the manuscript are satisfactory. Given the clarification and changes made to the new version, I recommend the publication of this work in SciPost.

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