Terahertz thermal spectroscopy of a NbN superconductor

Tesař, R.; Šindler, Michal; Ilin, K.; Koláček, Jan; Siegel, M.; Skrbek, L.

doi:10.1103/physrevb.84.132506

Cited by 9 publications

(5 citation statements)

References 14 publications

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“…In zero magnetic field the value of the superconducting gap was determined from the normalized tunneling conductance. The ratio 2∆(0)/k B T c was observed to vary from 4.25 to 4.5 along the surface of the sample; these values are slightly higher than what is typically observed [4,13,[32][33][34], nevertheless even higher values were also found [35]. These values suggest NbN is a strong-coupling superconductor and that, in general, high-frequency (THz) response should be treated within the framework of Eliashberg formulas following Nam [36,37].…”

Section: A Sources Of Errorsmentioning

confidence: 84%

Far-infrared electrodynamics of thin superconducting NbN film in magnetic fields

Šindler

Tesař

Koláček

et al. 2014

Supercond. Sci. Technol.

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We studied a thin superconducting NbN film in magnetic fields up to 8 T above the zerotemperature limit by means of time-domain terahertz and scanning tunneling spectroscopies in order to understand the vortex response. Scanning tunneling spectroscopy was used to determine the optical gap and the upper critical field of the sample. The obtained values were subsequently used to fit the terahertz complex conductivity spectra in the magnetic field in the Faraday geometry above the zero temperature limit. These spectra are best described in terms of the Coffey-Clem self-consistent solution of a modified London equation in the flux creep regime. 74.25.Gz, 74.55.+v,

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Section: A Sources Of Errorsmentioning

confidence: 84%

Far-infrared electrodynamics of thin superconducting NbN film in magnetic fields

Šindler

Tesař

Koláček

et al. 2014

Supercond. Sci. Technol.

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“…Also the transmission maximum becomes significantly lower. Recently, it was shown [87,88] that when the superconducting state is suppressed by a magnetic field, this transmission maximum broadens and shifts to lower temperatures. This is in agreement with the fact that the maximum in transmission corresponds to the energy gap.…”

Section: Energy Gapmentioning

confidence: 99%

Electrodynamics of Metallic Superconductors

Dressel

2013

Advances in Condensed Matter Physics

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The theoretical and experimental aspects of the microwave, terahertz, and infrared properties of superconductors are discussed. Electrodynamics can provide information about the superconducting condensate as well as about the quasiparticles. The aim is to understand the frequency dependence of the complex conductivity, the change with temperature and time, and its dependence on material parameters. We confine ourselves to conventional metallic superconductors, in particular, Nb and related nitrides and review the seminal papers but also highlight latest developments and recent experimental achievements. The possibility to produce well-defined thin films of metallic superconductors that can be tuned in their properties allows the exploration of fundamental issues, such as the superconductor-insulator transition; furthermore it provides the basis for the development of novel and advanced applications, for instance, superconducting single-photon detectors.

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“…The deviation between the simulated and measured extinction spectra at Fano resonance frequency arises due to the anisotropic dispersion of the r-cut sapphire substrate and fabrication imperfections. [34] Detailed information about the effect of the substrate permittivity on the extinction spectra and the robustness of anapole against sapphire's permittivity are provided in Figure S5 (Supporting Information). The dynamic switching of anapole mode to Fano I resonance is also observed in the simulation results (lower panel of Figure 4b).…”

Section: Resultsmentioning

confidence: 99%

Photoswitchable Anapole Metasurfaces

Wang

Srivastava

Gupta

et al. 2021

Advanced Optical Materials

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The electromagnetic response of matter can be described by the electric, magnetic, and toroidal multipole families, which mainly originate from oscillating charges, loop currents, and poloidal currents, respectively. Tailoring the interplay between different multipoles is an efficient approach to control the electromagnetic radiation characteristics. For example, a directive radiation pattern without backscattering could be obtained by balancing the electric dipole (ED) and magnetic dipole (MD), known as the Kerker condition, [3] which has been generalized for higher-order multipoles. [4] The destructive interference of ED and toroidal dipole (TD) yields an exotic nonradiating anapole mode. The term anapole (meaning "without poles" in Greek) was first introduced in nuclear physics by Zel'dovich in 1957 to describe the non-interaction of elementary particles and external electromagnetic fields. [5] It was then generalized to electrodynamics and was first observed at microwave frequencies in 2013. [6] As ED and TD present identical far-field radiation patterns, the total radiation is suppressed when the two modes are excited with the same radiation magnitude but out of phase, giving rise to the electrodynamic analogy of anapole. The nontrivial nonradiating feature of anapole is also accompanied by strong field confinement in the matter. These unique properties endow potential of anapole in the applications of cloaking, [7,8] lasers, [9] and nonlinear enhancement. [10][11][12] Active control of the light-matter interactions, including the engineered far-field radiation and near-field enhancement, is desired for modern multifunctional photonic devices. For instance, terahertz (THz) communication requires high-contrast THz amplitude modulation at ultrafast speed, [13,14] and dynamic near-field imaging requires active tuning of near-field intensity. [15] However, most of the current anapole-assisted works show passive control by modifying the structure configuration, [16,17] in which the device's functionality is fixed after fabrication and cannot be changed afterward. A recent study demonstrates active mode shift utilizing phase-change alloy Ge 2 Sb 2 Te 5 (GST). [18] By altering the GST from crystalline phase to amorphous phase, the dark anapole mode is switched to the bright ED mode in several minutes. More efficient control of anapole mode will add new building blocks of meta-optics and further extend the functionalities of anapole-based active photonic devices.Nonradiating charge-current configurations have attracted attention in photonics for the efficient localization of the electromagnetic field. Anapole mode is a unique nonradiating state of light induced by the interference of electric and toroidal dipole that possesses rich physics with potential applications in micro-nanophotonics. Active control of an anapole is essential for the design and realization of tunable low-energy photonic devices. Here, an active anapole metasurface device is experimentally demonstrated as a switch for the terahertz waves. The m...

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Terahertz thermal spectroscopy of a NbN superconductor

Cited by 9 publications

References 14 publications

Far-infrared electrodynamics of thin superconducting NbN film in magnetic fields

Far-infrared electrodynamics of thin superconducting NbN film in magnetic fields

Electrodynamics of Metallic Superconductors

Photoswitchable Anapole Metasurfaces

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