The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band
de, Visser PJ
Applied Physics Letters
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de, V. P., Yates, S., Guruswamy, T., Goldie, D., Withington, S., Neto, A., Llombart, N., et al. (2015). The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band. Applied Physics Letters, 106 (252602)https://doi.org/10.1063/1.4923097
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.
Collective excitations, Antennas, Superconductors, Tantalum, Phonons
We would like to thank Jan Barkhof for help with the FTS calibration. This work was in part supported by ERC starting Grant Nos. ERC-2009-StG and 240602 TFPA. T. M. Klapwijk acknowledges financial support from the Ministry of Science and Education of Russia under Contract No. 14.B25.31.0007 and from the European Research Council Advanced Grant No. 339306 (METIQUM). P. J. de Visser acknowledges support from a Niels Stensen Fellowship.
External DOI: https://doi.org/10.1063/1.4923097
This record's URL: https://www.repository.cam.ac.uk/handle/1810/253064