A superconductor free of quasiparticles for seconds

Elsa T. Mannila (Corresponding Author), Peter Samuelsson, Slawomir Simbierowicz, J.T. Peltonen, Visa Vesterinen, Leif Grönberg, Juha Hassel, Ville F. Maisi, J.P. Pekola

Research output: Contribution to journalArticleScientificpeer-review

19 Citations (Scopus)

Abstract

Superconducting devices, based on the Cooper pairing of electrons, play an important role in existing and emergent technologies, ranging from radiation detectors to quantum computers. Their performance is limited by spurious quasiparticle excitations formed from broken Cooper pairs. Efforts to achieve ultra-low quasiparticle densities have reached time-averaged numbers of excitations on the order of one in state-of-the-art devices. However, the dynamics of the quasiparticle population as well as the timescales for adding and removing individual excitations remain largely unexplored. Here, we experimentally demonstrate a superconductor completely free of quasiparticles for periods lasting up to seconds. We monitor the quasiparticle number on a mesoscopic superconductor in real time by measuring the charge tunnelling to a normal metal contact. Quiet, excitation-free periods are interrupted by random-in-time Cooper pair breaking events, followed by a burst of charge tunnelling within a millisecond. Our results demonstrate the possibility of operating devices without quasiparticles with potentially improved performance. In addition, our experiment probes the origins of nonequilibrium quasiparticles in our device. The decay of the Cooper pair breaking rate over several weeks following the initial cooldown rules out processes arising from cosmic or long-lived radioactive sources.
Original languageEnglish
Pages (from-to)145-148
JournalNature Physics
Volume18
Issue number2
DOIs
Publication statusPublished - 20 Dec 2021
MoE publication typeA1 Journal article-refereed

Funding

This work was performed as part of the Academy of Finland Centre of Excellence program (projects 312057, 312059 and 312294). We acknowledge the provision of facilities and technical support by Aalto University at OtaNano - Micronova Nanofabrication Centre and OtaNano - Low Temperature Laboratory. E.T.M. and J.P.P. acknowledge financial support from Microsoft. V.V. acknowledges financial support from the Academy of Finland through grant no. 321700. P.S. and V.F.M. acknowledge financial support from the Swedish National Science Foundation, and V.F.M. acknowledges financial support from the QuantERA project ‘2D hybrid materials as a platform for topological quantum computing’ and NanoLund.

Keywords

  • superconducting properties and materials
  • superconducting devices

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