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Conductance asymmetries in mesoscopic superconducting devices due to finite bias

by André Melo, Chun-Xiao Liu, Piotr Rożek, Tómas Örn Rosdahl, Michael Wimmer

Submission summary

As Contributors: André Melo · Michael Wimmer
Arxiv Link: (pdf)
Code repository:
Data repository:
Date accepted: 2021-02-02
Date submitted: 2021-01-28 10:52
Submitted by: Melo, André
Submitted to: SciPost Physics
Academic field: Physics
  • Condensed Matter Physics - Theory
Approaches: Theoretical, Computational


Tunneling conductance spectroscopy in normal metal-superconductor junctions is an important tool for probing Andreev bound states in mesoscopic superconducting devices, such as Majorana nanowires. In an ideal superconducting device, the subgap conductance obeys specific symmetry relations, due to particle-hole symmetry and unitarity of the scattering matrix. However, experimental data often exhibits deviations from these symmetries or even their explicit breakdown. In this work, we identify a mechanism that leads to conductance asymmetries without quasiparticle poisoning. In particular, we investigate the effects of finite bias and include the voltage dependence in the tunnel barrier transparency, finding significant conductance asymmetries for realistic device parameters. It is important to identify the physical origin of conductance asymmetries: in contrast to other possible mechanisms such as quasiparticle poisoning, finite-bias effects are not detrimental to the performance of a topological qubit. To that end we identify features that can be used to experimentally determine whether finite-bias effects are the source of conductance asymmetries.

Published as SciPost Phys. 10, 037 (2021)

Author comments upon resubmission

Minor changes to address the referee reports and a correction in the analytical calculations of section 3. See "List of Changes" for more details.

List of changes

- Corrected the $W$ matrix (eq. 13) to ensure it has particle-hole symmetry. While this change leads to a different expression for the intermediate result in eq. 14, all other results remain valid.
- Added clarification and fixes mentioned in replies to referee reports.

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