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Subgap transport in superconductor-semiconductor hybrid islands : Weak and strong coupling regimes

Valentini, Marco ; Souto, Rubén Seoane LU orcid ; Borovkov, Maksim ; Krogstrup, Peter ; Meir, Yigal ; Leijnse, Martin LU ; Danon, Jeroen and Katsaros, Georgios (2025) In Physical Review Research 7(2).
Abstract

Superconductor-semiconductor hybrid systems play a crucial role in realizing nanoscale quantum devices, including hybrid qubits, Majorana bound states, and Kitaev chains. For such hybrid devices, subgap states play a prominent role in their operation. In this paper, we study these subgap states via Coulomb and tunneling spectroscopy through a superconducting island defined in a semiconductor nanowire fully coated by a superconductor. We systematically explore regimes ranging from an almost decoupled island to the open configuration. In the weak-coupling regime, the experimental observations are very similar in the absence of a magnetic field and when one flux quantum pierces the superconducting shell. Conversely, in the strong-coupling... (More)

Superconductor-semiconductor hybrid systems play a crucial role in realizing nanoscale quantum devices, including hybrid qubits, Majorana bound states, and Kitaev chains. For such hybrid devices, subgap states play a prominent role in their operation. In this paper, we study these subgap states via Coulomb and tunneling spectroscopy through a superconducting island defined in a semiconductor nanowire fully coated by a superconductor. We systematically explore regimes ranging from an almost decoupled island to the open configuration. In the weak-coupling regime, the experimental observations are very similar in the absence of a magnetic field and when one flux quantum pierces the superconducting shell. Conversely, in the strong-coupling regime, significant distinctions emerge between the two cases. We attribute this distinct behavior to the existence of subgap states at one flux quantum, which become observable only for sufficiently strong coupling to the leads. We support our interpretation using a simple model to describe transport through the island. Our study highlights the importance of studying a broad range of tunnel couplings for understanding the rich physics of hybrid devices.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review Research
volume
7
issue
2
article number
023022
publisher
American Physical Society
external identifiers
  • scopus:105002322839
ISSN
2643-1564
DOI
10.1103/PhysRevResearch.7.023022
language
English
LU publication?
yes
id
6532d2bf-fa70-43e3-b0e9-56f96eb520e3
date added to LUP
2025-08-25 12:42:36
date last changed
2025-10-14 12:57:57
@article{6532d2bf-fa70-43e3-b0e9-56f96eb520e3,
  abstract     = {{<p>Superconductor-semiconductor hybrid systems play a crucial role in realizing nanoscale quantum devices, including hybrid qubits, Majorana bound states, and Kitaev chains. For such hybrid devices, subgap states play a prominent role in their operation. In this paper, we study these subgap states via Coulomb and tunneling spectroscopy through a superconducting island defined in a semiconductor nanowire fully coated by a superconductor. We systematically explore regimes ranging from an almost decoupled island to the open configuration. In the weak-coupling regime, the experimental observations are very similar in the absence of a magnetic field and when one flux quantum pierces the superconducting shell. Conversely, in the strong-coupling regime, significant distinctions emerge between the two cases. We attribute this distinct behavior to the existence of subgap states at one flux quantum, which become observable only for sufficiently strong coupling to the leads. We support our interpretation using a simple model to describe transport through the island. Our study highlights the importance of studying a broad range of tunnel couplings for understanding the rich physics of hybrid devices.</p>}},
  author       = {{Valentini, Marco and Souto, Rubén Seoane and Borovkov, Maksim and Krogstrup, Peter and Meir, Yigal and Leijnse, Martin and Danon, Jeroen and Katsaros, Georgios}},
  issn         = {{2643-1564}},
  language     = {{eng}},
  number       = {{2}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review Research}},
  title        = {{Subgap transport in superconductor-semiconductor hybrid islands : Weak and strong coupling regimes}},
  url          = {{http://dx.doi.org/10.1103/PhysRevResearch.7.023022}},
  doi          = {{10.1103/PhysRevResearch.7.023022}},
  volume       = {{7}},
  year         = {{2025}},
}