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Measuring coherence factors of states in superconductors through local current

Dourado, Rodrigo A. ; Danon, Jeroen ; Leijnse, Martin LU and Souto, Rubén Seoane LU orcid (2025) In Physical Review B 112(17).
Abstract
The coherence factors of quasiparticles in a superconductor determine their properties, including transport as well as their susceptibility to electric fields. In this work, we propose a way to infer the local coherence factors using local transport to normal leads. Our method is based on measuring the local current through a lead as the coupling to a second one is varied; the shape of the current is determined by the ratio between the local coherence factors, becoming independent of the coupling to the second lead in the presence of local electron-hole symmetry, i.e., coherence factors ||=||. We apply our method to minimal Kitaev chains: arrays of quantum dots coupled via narrow superconducting segments. These chains feature Majorana-like... (More)
The coherence factors of quasiparticles in a superconductor determine their properties, including transport as well as their susceptibility to electric fields. In this work, we propose a way to infer the local coherence factors using local transport to normal leads. Our method is based on measuring the local current through a lead as the coupling to a second one is varied; the shape of the current is determined by the ratio between the local coherence factors, becoming independent of the coupling to the second lead in the presence of local electron-hole symmetry, i.e., coherence factors ||=||. We apply our method to minimal Kitaev chains: arrays of quantum dots coupled via narrow superconducting segments. These chains feature Majorana-like quasiparticles (zero-energy states with ||=||) at discrete points in parameter space. We demonstrate that the local current allows us to estimate the local Majorana polarization (MP)—a measurement of the local Majorana properties of the state. We derive an analytical expression for the MP in terms of local currents and benchmark it against numerical calculations for two- and three-sites chains that include a finite Zeeman field and electron-electron interactions. These results provide a way to quantitatively assess the quality of Majorana states in short Kitaev chains. (Less)
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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
112
issue
17
article number
174515
publisher
American Physical Society
ISSN
2469-9950
DOI
10.1103/wx5x-vpf7
language
English
LU publication?
yes
id
8247619a-5d78-498f-b33b-8eebc4729b7f
date added to LUP
2026-01-12 09:10:51
date last changed
2026-01-13 09:54:16
@article{8247619a-5d78-498f-b33b-8eebc4729b7f,
  abstract     = {{The coherence factors of quasiparticles in a superconductor determine their properties, including transport as well as their susceptibility to electric fields. In this work, we propose a way to infer the local coherence factors using local transport to normal leads. Our method is based on measuring the local current through a lead as the coupling to a second one is varied; the shape of the current is determined by the ratio between the local coherence factors, becoming independent of the coupling to the second lead in the presence of local electron-hole symmetry, i.e., coherence factors ||=||. We apply our method to minimal Kitaev chains: arrays of quantum dots coupled via narrow superconducting segments. These chains feature Majorana-like quasiparticles (zero-energy states with ||=||) at discrete points in parameter space. We demonstrate that the local current allows us to estimate the local Majorana polarization (MP)—a measurement of the local Majorana properties of the state. We derive an analytical expression for the MP in terms of local currents and benchmark it against numerical calculations for two- and three-sites chains that include a finite Zeeman field and electron-electron interactions. These results provide a way to quantitatively assess the quality of Majorana states in short Kitaev chains.}},
  author       = {{Dourado, Rodrigo A. and Danon, Jeroen and Leijnse, Martin and Souto, Rubén Seoane}},
  issn         = {{2469-9950}},
  language     = {{eng}},
  month        = {{11}},
  number       = {{17}},
  publisher    = {{American Physical Society}},
  series       = {{Physical Review B}},
  title        = {{Measuring coherence factors of states in superconductors through local current}},
  url          = {{http://dx.doi.org/10.1103/wx5x-vpf7}},
  doi          = {{10.1103/wx5x-vpf7}},
  volume       = {{112}},
  year         = {{2025}},
}