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Majorana modes in quantum dots coupled via a floating superconducting island

Souto, Rubén Seoane LU orcid ; Baran, Virgil V. ; Nitsch, Maximilian LU orcid ; Maffi, Lorenzo ; Paaske, Jens ; Leijnse, Martin LU and Burrello, Michele (2025) In Physical Review B 111(17).
Abstract

Majorana modes can be engineered in arrays where quantum dots (QDs) are coupled via grounded superconductors, effectively realizing an artificial Kitaev chain. Minimal Kitaev chains, composed by two QDs, can host fully localized Majorana modes at discrete points in parameter space, known as Majorana sweet spots. Unlike grounded superconductors, where the superconducting phase is a conserved quantum number, floating islands have a well-defined number of charges. The coexistence of charging effects and Majorana physics allows us to explore novel phenomenology, including teleportation and topological Kondo effect. Here, we extend previous works by theoretically investigating a setup with two QDs coupled via a floating superconducting... (More)

Majorana modes can be engineered in arrays where quantum dots (QDs) are coupled via grounded superconductors, effectively realizing an artificial Kitaev chain. Minimal Kitaev chains, composed by two QDs, can host fully localized Majorana modes at discrete points in parameter space, known as Majorana sweet spots. Unlike grounded superconductors, where the superconducting phase is a conserved quantum number, floating islands have a well-defined number of charges. The coexistence of charging effects and Majorana physics allows us to explore novel phenomenology, including teleportation and topological Kondo effect. Here, we extend previous works by theoretically investigating a setup with two QDs coupled via a floating superconducting island. We study the effects of the charging energy of the island and the properties of the resulting minimal Kitaev chain. We initially employ a minimal perturbative model, valid in the weak QD-island coupling regime, to derive analytic expressions for the Majorana sweet spots and the splitting of the ground-state degeneracy as a function of tunable physical parameters. The conclusions from this perturbative approximation are then benchmarked using a microscopic model that explicitly describes the internal degrees of freedom of the island. Our work shows the existence of Majorana sweet spots, even when the island is not tuned at a charge-degeneracy point. In contrast to the Kitaev chains in grounded superconductors, these sweet spots involve a degeneracy between states with a well-defined number of particles and allow us to explore the interplay between Majorana states and charging effects.

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author
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organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical Review B
volume
111
issue
17
article number
174501
publisher
American Physical Society
external identifiers
  • scopus:105004173086
ISSN
2469-9950
DOI
10.1103/PhysRevB.111.174501
language
English
LU publication?
yes
id
c636e985-8136-4701-9751-5ef02259e680
date added to LUP
2025-08-11 13:33:57
date last changed
2025-08-11 13:34:07
@article{c636e985-8136-4701-9751-5ef02259e680,
  abstract     = {{<p>Majorana modes can be engineered in arrays where quantum dots (QDs) are coupled via grounded superconductors, effectively realizing an artificial Kitaev chain. Minimal Kitaev chains, composed by two QDs, can host fully localized Majorana modes at discrete points in parameter space, known as Majorana sweet spots. Unlike grounded superconductors, where the superconducting phase is a conserved quantum number, floating islands have a well-defined number of charges. The coexistence of charging effects and Majorana physics allows us to explore novel phenomenology, including teleportation and topological Kondo effect. Here, we extend previous works by theoretically investigating a setup with two QDs coupled via a floating superconducting island. We study the effects of the charging energy of the island and the properties of the resulting minimal Kitaev chain. We initially employ a minimal perturbative model, valid in the weak QD-island coupling regime, to derive analytic expressions for the Majorana sweet spots and the splitting of the ground-state degeneracy as a function of tunable physical parameters. The conclusions from this perturbative approximation are then benchmarked using a microscopic model that explicitly describes the internal degrees of freedom of the island. Our work shows the existence of Majorana sweet spots, even when the island is not tuned at a charge-degeneracy point. In contrast to the Kitaev chains in grounded superconductors, these sweet spots involve a degeneracy between states with a well-defined number of particles and allow us to explore the interplay between Majorana states and charging effects.</p>}},
  author       = {{Souto, Rubén Seoane and Baran, Virgil V. and Nitsch, Maximilian and Maffi, Lorenzo and Paaske, Jens and Leijnse, Martin and Burrello, Michele}},
  issn         = {{2469-9950}},
  language     = {{eng}},
  number       = {{17}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review B}},
  title        = {{Majorana modes in quantum dots coupled via a floating superconducting island}},
  url          = {{http://dx.doi.org/10.1103/PhysRevB.111.174501}},
  doi          = {{10.1103/PhysRevB.111.174501}},
  volume       = {{111}},
  year         = {{2025}},
}