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arXiv · 2507.03217

Can slow recombination in ordered superconductors explain the excess quasiparticle population?

Eva Gurra·Douglas A. Bennett·Shannon M. Duff·Michael R. Vissers·Joel N. Ullom
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Abstract

An excess density of quasiparticles is widely observed in superconducting films. This excess causes performance degradation in a variety of superconducting devices, including decoherence in qubits. In this Letter, we evaluate the hypothesis of [1] that the quasiparticle excess is caused by anomalously slow recombination at low quasiparticle densities due to localization in sub-gap states. We probe the density of states in aluminum and niobium films using current-voltage measurements of tunnel junctions and extract upper bounds on the energy scales of the sub-gap states and gap smearing. With these parameters, we evaluate the recombination times predicted by [1] and find that slow recombination is not predicted to occur at observed quasiparticle densities in aluminumand niobium-based superconducting devices. These results suggest that the quasiparticle excess in ordered superconductors is primarily due to non-thermal sources of quasiparticle generation and not slow recombination.

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Eva Gurra, Douglas A. Bennett, Shannon M. Duff, Michael R. Vissers, Joel N. Ullom. 2025-07-03. Can slow recombination in ordered superconductors explain the excess quasiparticle population?. https://arxiv.org/abs/2507.03217

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