SciPost Submission Page
Light-induced Floquet spin-triplet Cooper pairs in unconventional magnets
by Pei-Hao Fu, Sayan Mondal, Jun-Feng Liu, Jorge Cayao
Submission summary
| Authors (as registered SciPost users): | Jorge Cayao |
| Submission information | |
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| Preprint Link: | scipost_202508_00016v1 (pdf) |
| Date submitted: | Aug. 6, 2025, 10:05 a.m. |
| Submitted by: | Jorge Cayao |
| Submitted to: | SciPost Physics |
| Ontological classification | |
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| Academic field: | Physics |
| Specialties: |
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| Approach: | Theoretical |
Abstract
The recently predicted unconventional magnets offer a new ground for exploring the formation of nontrivial spin states due to their inherent nonrelativistic momentum-dependent spin splitting. In this work, we consider unconventional magnets with $d$- and $p$-wave parities, and investigate the effect of time-periodic light drives for inducing the formation of spin-triplet phases in the normal and superconducting states. In particular, we consider unconventional magnets without and with conventional superconductivity under linearly and circularly polarized light drives and treat the time-dependent problem within Floquet formalism, which naturally unveils photon processes and Floquet bands determining the emergent phenomena. We demonstrate that the interplay between unconventional magnetism and light gives rise to a non-trivial light-matter coupling which governs the emergence of Floquet spin-triplet states with and without superconductivity that are absent otherwise. We find that photon-assisted processes promote the formation of spin-triplet densities and spin-triplet Cooper pairs between different Floquet sidebands. More precisely, the Floquet sidebands offer an additional quantum number, the Floquet index, which considerably broadens the classification of superconducting correlations that lead to Floquet spin-triplet Cooper pairs as an entirely dynamical phenomenon due to the interplay between light and unconventional magnetism. Furthermore, we discuss how the number of photons is connected to the symmetry of Cooper pairs and also explore how the distinct light drives can be used to manipulate them and probe the angular symmetry of unconventional magnets. Our results therefore unveil the potential of unconventional magnets for realizing nontrivial light-induced superconducting states.
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
Current status:
Reports on this Submission
Report
In this manuscript, the authors address how time-periodic light drives (circularly and linearly polarized light) induce Floquet spin-triplet densities and Floquet spin-triplet Cooper pairs in unconventional magnets with $p$- and $d$-wave parity, especially $p_{x}$ and $d_{x^2-y^2}$. Using Floquet theory and BdG formalism, the authors identify photon-induced processes that generate new pairing symmetries absent in equilibrium. The topic is timely and relevant to Floquet-engineered quantum systems and unconventional magnetism.
In the appendix, the authors provide a section entitled “Hamiltonian and Floquet components in higher-order-momentum unconventional magnet.” I really appreciate this section.
The manuscript is well written and technically solid, but several points require clarification or further justification before publication.
Major and minor comments:
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Could the author explain how to write the effective model involving two arbitrary Floquet sidebands, i.e., Eq.(39)?
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How many Floquet sidebands were kept in the calculations, and how did the authors ensure convergence of the spin density and pairing amplitudes?
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Could the authors comment on whether the Floquet triplet states would survive in a realistic Floquet heating effect?
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Is there any simple physical explanation for why odd-photon processes produce purely light-induced pairing channels, while even-photon processes can mix with static correlations? Is it stable against disorder?
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Resolution of a few figures (Fig. 3 and 4, for example) should be increased for clarity.
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There are a few recent studies on Floquet in altermagnetic systems [eg, Phys. Rev. B 112, L201408 (2025)]. The author should cite those articles accordingly.
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Is it possible to relate Floquet spin-triplet density to any experimental observable?
Typos to be fixed:
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In page number 7, below Eq.(4), they have written "while a $p_x$-wave magnet for $\theta_J = \frac{\pi}{2}$." It should be "while a $p_y$-wave magnet for $\theta_J = \frac{\pi}{2}$."
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In Eq.(40), the authors should keep space in between 2 and $\delta n$ and no space between $\delta$ and $n$. The correct form seems to be $\delta$ times $n$, rather than $\delta n$.
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In Fig. 4, panels (b) and (c) should be interchanged to be consistent with the figure caption and explanation in the main text.
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A few spelling typos are also there.
Requested changes
Modify the figures and add possible explanations according to the report.
Recommendation
Ask for minor revision
Strengths
2.easy to follw
3.pleasant to read
4.the idea behind it is intriguing
5.the results are rich and well presented
6.the formalism used is described in a transparent and informative way.
Weaknesses
2.the limitations of the formalism are not stated (what about heating, Floquet band occupation,..)
Report
Requested changes
Add a discussion about the observability of the effects.
Recommendation
Publish (easily meets expectations and criteria for this Journal; among top 50%)