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  • Letter
  • Open Access

Excess quasiparticles and their dynamics in the presence of subgap states

P. B. Fischer1,2 and G. Catelani1,3

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Phys. Rev. B 112, L100507 – Published 26 September, 2025

DOI: https://doi.org/10.1103/jj9b-27qs

Abstract

Material inhomogeneities in a superconductor generically lead to broadening of the density of states and to subgap states. The latter are associated with spatial fluctuations of the gap in which quasiparticles can be trapped. Recombination between such localized quasiparticles is hindered by their spatial separation and hence their density could be higher than expectations based on the recombination between mobile quasiparticles. We show here that the recombination between localized and mobile excitations can be efficient at limiting the quasiparticle density. We comment on the significance of our findings for devices such as superconducting resonators and qubits. We find that for typical aluminum devices, the subgap states do not significantly influence the quasiparticle density.

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Phys. Rev. B 112, L100507– Published 26 September, 2025
  • Received 13 May 2025
  • Accepted 10 September 2025
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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