The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band

de Visser, P. J., Yates, S. J. C., Guruswamy, T., Goldie, D. J., Withington, S., Neto, A., Llombart, N., Baryshev, A. M., Klapwijk, T. M. & Baselmans, J. J. A., Jun-2015, In : Applied Physics Letters. 106, 25, 6 p., 252602.

Research output: Contribution to journalArticleAcademicpeer-review

  • P. J. de Visser
  • S. J. C. Yates
  • T. Guruswamy
  • D. J. Goldie
  • S. Withington
  • A. Neto
  • N. Llombart
  • A. M. Baryshev
  • T. M. Klapwijk
  • J. J. A. Baselmans
We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on, the response drops to half the maximum response at twice the pair-breaking energy. At higher frequencies, the response rises again due to trapping of pair-breaking phonons in the superconductor. In practice, this is a measurement of the frequency dependence of the quasiparticle creation efficiency due to pair-breaking in a superconductor. The efficiency, calculated from the different non-equilibrium quasiparticle distribution functions at each frequency, is in agreement with the measurements.
Original languageEnglish
Article number252602
Number of pages6
JournalApplied Physics Letters
Issue number25
Publication statusPublished - Jun-2015



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