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Mean-field theory of first-order quantum superconductor-insulator transition
by Igor Poboiko, Mikhail Feigel'man
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Submission summary
| Authors (as registered SciPost users): | Mikhail Feigel'man · Igor Poboiko |
| Submission information | |
|---|---|
| Preprint Link: | https://arxiv.org/abs/2405.08571v2 (pdf) |
| Date accepted: | 2024-08-07 |
| Date submitted: | 2024-05-27 12:05 |
| Submitted by: | Poboiko, Igor |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Recent experimental studies on strongly disordered indium oxide films have revealed an unusual first-order quantum phase transition between the superconducting and insulating states (SIT). This transition is characterized by a discontinuous jump from non-zero to zero values of superfluid stiffness at the critical point, contradicting the conventional ``scaling scenario'' typically associated with SIT. In this paper, we present a theoretical framework for understanding this first-order transition. Our approach is based on the concept of competition between two fundamentally distinct ground states that arise from electron pairs initially localized by strong disorder: the superconducting state and the Coulomb glass insulator. These ground states are distinguished by two crucially different order parameters, suggesting a natural expectation of a discontinuous transition between them at $T=0$. This transition occurs when the magnitudes of the superconducting gap $\Delta$ and the Coulomb gap $E_C$ become comparable. Additionally, we extend our analysis to low non-zero temperatures and provide a mean-field ``phase diagram'' in the plane of $(T/\Delta,E_C/\Delta)$. Our results reveal the existence of a natural upper bound for the kinetic inductance of strongly disordered superconductors.
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
Published as SciPost Phys. 17, 066 (2024)
Reports on this Submission
Strengths
The paper by Poboiko and Feigel’man present a theory of first-order insulator to superconductor transition, a feature already observed in experiments. The model put forward and analyzed by the authors consists in tightly bound pairs hopping in a disordered medium with an additional Coulomb repulsion between the pairs. The detailed analysis confirms the possibility of an abrupt transition with an experimentally accessible predictions related to the upper bound of the kinetic inductance.
I find the paper very nicely written, it contains a very useful discussion on the physical concepts underlying the model and a detailed analysis of its consequences. The calculations and approximations used are discussed very clear.
I find the paper very solid.
Weaknesses
I did not spot any evident weakness
Report
As explained above, I find the paper very interesting, ready for the publication.
Requested changes
no requested changes
Recommendation
Publish (surpasses expectations and criteria for this Journal; among top 10%)
Strengths
The manuscript provides a detailed consistent description of the transition between a Coulomb gap state and a superconductor. Within certain approximations (such as neglecting single particle excitations and assuming a uniform \Delta) the authors found the transition to be of the first order. I found this conclusion reasonable and well justified (possibly even beyond the adopted approximations).
The manuscript is well written and contains technical appendixes, clarifying most of technical questions.
Weaknesses
There are no obvious weaknesses.
Report
The paper is highly significant for the experimentally and theoretically important subject of superconductor-insulator quantum phase transition. I found it to be comprehensive and likely correct. I suggest to publish the manuscript.
Requested changes
As an optional change, I'd ask the author to expand their discussion of using replica symmetric solution within the superconducting state. Why is it justified by the weakness of the Coulomb interactions? Can one in principle imagine RSB superconducting state? What observable consequences it may have?
Recommendation
Publish (surpasses expectations and criteria for this Journal; among top 10%)