Abstract-Departure from BCS response in photoexcited superconducting NbN films observed by terahertz spectroscopy

M. Šindler, C. Kadlec, P. Kužel, K. Ilin, M. Siegel, and H. Němec

https://journals.aps.org/prb/abstract/10.1103/PhysRevB.97.054507

We investigate time-resolved terahertz conductivity of thin superconducting NbN films with various thicknesses upon their excitation by intense femtosecond laser pulses. The recovery dynamics following a complete destruction of the superconducting state occurs via a growth of superconducting islands in the normal-state environment. This is in contrast with previous observations of the recovery upon strong-field terahertz excitation [R. Matsunaga and R. Shimano, Phys. Rev. Lett. 109, 187002 (2012)]. We observe that the density of electronic states in the superconducting islands deviates from the BCS theory predictions on a subnanosecond time scale, while equilibrium terahertz conductivity spectra confirm the standard BCS behavior in the ground state.

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Abstract-Bulk magnetic terahertz metamaterials based on dielectric microspheres

Bulk magnetic terahertz metamaterials based on dielectric microspheres 

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-24-16-18340

M. Šindler, C. Kadlec, F. Dominec, P. Kužel, C. Elissalde, A. Kassas, J. Lesseur, D. Bernard, P. Mounaix, and H. Němec

Rigid metamaterials were prepared by embedding TiO2 microspheres into polyethylene. These structures exhibit a series of Mie resonances where the lowest-frequency one is associated with a strong dispersion in the effective magnetic permeability. Using time-domain terahertz spectroscopy, we experimentally demonstrated the magnetic nature of the observed resonance. The presented approach shows a way for low-cost massive fabrication of mechanically stable terahertz metamaterials based on dielectric microresonators.

© 2016 Optical Society of America

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