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Phase transitions in quantum dot-Majorana zero mode coupling systems
by Yue Mao, Qing-Feng Sun
This is not the latest submitted version.
Submission summary
| Authors (as registered SciPost users): | Yue Mao |
| Submission information | |
|---|---|
| Preprint Link: | scipost_202406_00024v1 (pdf) |
| Date submitted: | 2024-06-12 13:16 |
| Submitted by: | Mao, Yue |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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Abstract
The magnetic doublet ground state (GS) of quantum dot (QD) could be changed to a spin-singlet GS by coupling to a normal superconductor. In analogy, here we study the GS phase transitions in QD-Majorana zero mode (MZM) coupling systems: GS behaves phase transition versus intra-dot energy level and QD-MZM coupling strength. The phase diagrams of GS are obtained, for cases with and without Zeeman term. Along with the phase transition, we also study the change of spin feature and density of states. The properties of phase transition are understood via a mean-field picture.
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
Strengths
1. Provides analytical solution
Weaknesses
1. No discussion of relationship of results as compared to the large set of previous papers studying coupling of a quantum dot to a Majorana zero mode
2. Model seems overly simplified
3. No discussion of how to observe the effect in experiment
4. Role of lead seems not to add anything relevant in terms of physics
Report
The paper deals with the problem of theoretically computing the ground state of a quantum dot coupled to a Majorana zero mode.
I do appreciate that the authors provide analytical solutions to this problem. There are however several major problems with this manuscript:
1. There have been several publications earlier about coupling a Majorana bound state to a quantum dot, e.g. Refs. [22, 57] cited in the paper, or e.g. https://doi.org/10.1103/PhysRevB.96.201109 . The paper does not discuss at all how the results relate to any of the previous work.
2. The model studied seems too simple for me: (i) in principle a Majorana bound state can couple to both spins in the quantum dot (see Ref. [22]), and (ii) the authors neglect the coupling to the superconducting continuum (at finite energy!). These simplifications are not discussed.
3. I am also missing a discussion of experimental relevance of the findings. The authors talk about a phase transition, but in the end it's just about whether the ground state spin is up or down. What is the relevance of this?
4. The authors introduce a normal lead. However, in the approximation they use, the lead just gives a finite broadening to the states. To me, it seems just a complication to compute the Green's function - the eigenstates give exactly the same physical information.
Unless these problems are addressed, I cannot recommend publishing the paper in any of SciPost's journals.
Recommendation
Ask for major revision
Author: Yue Mao on 2024-09-05 [id 4739]
(in reply to Report 1 on 2024-08-21)We thank the referee for carefully reading our manuscript and the valuable report. We provide our response to the questions raised by the referee in the attached file.
Attachment:
reply_mzm_pt_1_0905.pdf