SciPost Submission Page
InP/GaSb core-shell nanowires: a novel hole-based platform with strong spin-orbit coupling for full-shell hybrid devices
by Andrea Vezzosi, Carlos Payá, Paweł Wójcik, Andrea Bertoni, Guido Goldoni, Elsa Prada, Samuel D. Escribano
Submission summary
| Authors (as registered SciPost users): | Samuel D. Escribano · Carlos Payá |
| Submission information | |
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| Preprint Link: | https://arxiv.org/abs/2405.07651v3 (pdf) |
| Date submitted: | 2024-12-18 07:13 |
| Submitted by: | D. Escribano, Samuel |
| Submitted to: | SciPost Physics |
| Ontological classification | |
|---|---|
| Academic field: | Physics |
| Specialties: |
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| Approaches: | Theoretical, Computational |
Abstract
Full-shell hybrid nanowires (NWs), structures comprising a superconductor shell that encapsulates a semiconductor (SM) core, have attracted considerable attention in the search for Majorana zero modes (MZMs). However, the predicted Rashba spin-orbit coupling (SOC) in the SM is too small to achieve substantial topological minigaps. In addition, the SM wavefunction spreads all across the section of the nanowire, leading typically to a finite background of trivial subgap states with which MZMs may coexist. To overcome both problems, we explore the advantages of utilizing core-shell hole-band NWs as the SM part of a full-shell hybrid, with an insulating core and an active SM shell. In particular, we consider InP/GaSb core-shell NWs, which allow to exploit the unique characteristics of the III-V compound SM valence bands. We demonstrate that they exhibit a robust hole SOC that emerges from the combination of the intrinsic spin-orbit interaction of the SM active shell and the confinement effects of the nanostructure, thus depending mainly on SM and geometrical parameters. In other words, the SOC is intrinsic and does not rely on red electric fields, which are non-tunable in a full-shell hybrid geometry. As a result, core-shell SM hole-band NWs are found to be a promising candidate to explore Majorana physics in full-hell hybrid devices, addressing several challenges in the field.
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
Thank you for giving us the opportunity to answer the last reports. We are also grateful to the Referees for their thoughtful feedback. We have revised the manuscript to address the remaining concerns raised by one of the Referees.
As you can see, two of the three Referees are satisfied with the previous changes and consider our work suitable for publication in SciPost Physics, highlighting its novelty and significance. The third Referee now acknowledges the correctness, clarity, and interest of our results, but remains unconvinced of the broader impact of our work. His/her primary concern relates to the similarity of the spin-orbit interaction (SOC) observed in our GaSb-InP nanodevice to that predicted for Ge-based nanowires.
While this observation is valid, we believe that the Referee (and perhaps also a general reader) may not be aware of the experimental challenges associated with Group IV nanowires, which limit their potential as a platform for realizing topological superconductivity. In contrast, our work introduces for the first time a nanowire design that takes advantage of the valence band properties (with strong SOC) of III-V semiconductor compounds. As many experimental groups exclusively work with III-V materials, particularly for the study of topological superconductivity precisely because of this reason, our proposal offers a realistic and accessible pathway for further exploration.
Furthermore, the significance of our work goes beyond the SOC strength. Our design incorporates an insulating core, which, although slightly diminishing the SOC, enables (i) wavefunction confinement close to the outer facet (where a potential superconductor would be placed), and (ii) partial tuning of the chemical potential — key requirements for achieving topological superconductivity.
To address these points, we have included an extended discussion comparing Group IV and III-V platforms to clarify the importance and implications of our proposal. Additionally, we have addressed all other minor comments from the Referee. As such, we believe that the manuscript clearly describes now its novelty and potential impact, and thus it should be suitable for publication in SciPost Physics.
Kind regards,
Samuel, on behalf of all the authors
List of changes
- References [27, 28] have been moved earlier in text (end of Section 1) and made clear that the SOC in our work is of the same kind than the one reported in these references. We have added a similar comment in the third paragraph of Section 3.3, when we describe the origin of the observed SOC.
- We have explained with more details the definition of SOC in our work at the end of the first paragraph in Section 3.2.
- We have added a more extended discussion about the experimental challenges of Ge-based heterostructures in the third paragraph of Section 2 (together with the footnote 3).
- We have removed all the comments about the fact that the SOC in Ge-based heterostructures depends on strain (as it is not completely true), including the abstract, Section 2, Section 4, and Appendix C.
- Several references have been added and updated.