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

Abstract

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 the first 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.

References in corpus (8)

• Number fluctuations of sparse quasiparticles in a superconductor
• Photon-noise limited sensitivity in titanium nitride kinetic inductance detectors
• Enhancement of quasiparticle recombination in Ta and Al superconductors by implantation of magnetic and nonmagnetic atoms
• Effect of Quasiparticles Injection on the AC Response of a Superconductor
• The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band
• Nonequilibrium superconducting thin films with sub-gap and pair-breaking photon illumination
• Equivalence of Optical and Electrical Noise Equivalent Power of Hybrid NbTiN-Al Microwave Kinetic Inductance Detectors
• Performance of Hybrid NbTiN-Al Microwave Kinetic Inductance Detectors as Direct Detectors for Sub-millimeter Astronomy

Cited by in corpus (6)

• Phonon-trapping enhanced energy resolution in superconducting single photon detectors
• Engineering physics of superconducting hot-electron bolometer mixers
• The non-equilibrium response of a superconductor to pair-breaking radiation measured over a broad frequency band
• Resolving Power of Visible to Near-Infrared Hybrid $\beta$-Ta/NbTiN Kinetic Inductance Detectors
• CCAT: Nonlinear effects in 280 GHz aluminum kinetic inductance detectors
• Magnetic field tunable spectral response of kinetic inductance detectors