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Quantum transport theory for unconventional magnets: Interplay of altermagnetism and p-wave magnetism with superconductivity
by Tim Kokkeler, Ilya Tokatly, F. Sebastian Bergeret
Submission summary
| Authors (as registered SciPost users): | F. Sebastian Bergeret · Tim Kokkeler · Ilya Tokatly |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2412.10236v3 (pdf) |
| Date accepted: | May 15, 2025 |
| Date submitted: | April 24, 2025, 7:44 a.m. |
| Submitted by: | Kokkeler, Tim |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Phenomenological |
Abstract
We present a quantum transport theory for generic magnetic metals, in which magnetism occurs predominantly due to exchange interactions, such as ferromagnets, antiferromagnets, altermagnets and p-wave magnets. Our theory is valid both for the normal and the superconducting state. We derive the effective low-energy action for each of these materials, where the spin space groups are used to determine the form of the tensor coefficients appearing in the action. The transport equations, which are obtained as the saddle point equations of this action, describe a wider range of phenomena than the usual quasiclassical equations. In ferromagnets, in addition to the usual exchange field and spin relaxation effects, we identify a spin-dependent renormalization of the diffusion coefficient, which provides a description of spinpolarized currents in both the normal and superconducting equal spin-triplet states. In the normal state, our equations provide a complete description of the spin-splitting effect in diffusive systems, recently predicted in ideal clean altermagnets. In the superconducting state, our equations predict a proximity induced magnetization, the appearance of a spontaneous magnetic moment in hybrid superconductor-altermagnet systems. The distribution and polarization direction of this magnetic moment depend on the symmetry of the structure, thus measurements of such polarization reveal the underlying microscopic symmetry of the altermagnet. Finally, for inversionsymmetry broken antiferromagnets, such as the p-wave magnet, we show that spin-galvanic effects which are distinguishable from the spin-galvanic effect induced by spin-orbit coupling only in the superconducting state. Besides these examples, our model applies to arbitrary magnetic systems, providing a complete theory for nonequilibrium transport in diffusive nonconventional magnets at arbitrary temperatures.
Author indications on fulfilling journal expectations
- Provide a novel and synergetic link between different research areas.
- Open a new pathway in an existing or a new research direction, with clear potential for multi-pronged follow-up work
- Detail a groundbreaking theoretical/experimental/computational discovery
- Present a breakthrough on a previously-identified and long-standing research stumbling block
Author comments upon resubmission
We would like to thank both referees for their careful examinations of the manuscript, their positive assessment of our article, and their suggestions which we could use to improve our manuscript. We have implemented all comments and suggested changes in the updated manuscript.
List of changes
A point by point overview of the changed is listed in the response to the Referees
Current status:
Editorial decision:
For Journal SciPost Physics: Publish
(status: Editorial decision fixed and (if required) accepted by authors)
Reports on this Submission
Report
In my opinion, the authors have addressed the concerns raised by the Referees satisfactorily in the revised version of the manuscript. I would recommend the publication of the present version (with minor corrections) in SciPost Physics.
Some minor issues to be addressed:
1) In Eq. (31), the matrix pair potential $\hat{\Delta}$ is missing in the first commutator. 2) I still think that there is a problem with formula (53). Compare it with the expression used in Eq. (C10) for the calculation of the charge supercurrent. 3) If Eq. (E20) is correct, the authors should then check Eq. (E14).
Recommendation
Publish (surpasses expectations and criteria for this Journal; among top 10%)