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-edge resonant inelastic x-ray scattering
摘要： We report an Fe L-edge resonant inelastic x-ray scattering (RIXS) study of the unusual superconductor β-FeSe. The high-energy resolution of this RIXS experiment (≈55 meV FWHM) made it possible to resolve low-energy excitations of the Fe 3d manifold. These include a broad peak which shows dispersive trends between 100 and 200 meV along the (π, 0) and (π, π) directions of the one-Fe square reciprocal lattice, and which can be attributed to paramagnon excitations. The multiband valence state of FeSe is among the most metallic in which such excitations have been discerned by soft x-ray RIXS.
关键词： RIXS,β-FeSe,Fe L-edge,dispersion,paramagnon,superconductor,resonant inelastic x-ray scattering
更新于2025-09-23 15:23:52
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One-Dimensional Metallo-Superconductor Photonic Crystals as a Smart Window
摘要： A new structure to control the electromagnetic waves has been successfully designed for smart windows applications. The present photonic crystals (PCs) smart window is designed from a unit cell of two different materials such as A (metal) and B (superconductor) of thicknesses that repeated for N periods. The numerical results are investigated based on the characteristic matrix method. It was found that the angle of incidence has a significant effect on the transmission values. At 10o angle of incidence, we found more than 80% of the visible light and a near IR is transmitted whereas at 60o angle of incidence, the photonic band gap (PBG) begins to appear at wavelengths greater than 800 nm and the visible light transmittance remains more than 80%. Also, the dependence of the transmittance values on the periodicity and thickness of the proposed design was investigated. The proposed structure could be of potential use as a smart window in low-temperature applications and space industry.
关键词： Photonic crystals,Smart window,Metal-superconductor
更新于2025-09-23 15:23:52
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Structural and Superconducting Properties of Thermal Treatment-Synthesised Bulk YBa2Cu3O7?δ Superconductor: Effect of Addition of SnO2 Nanoparticles
摘要： YBa2Cu3O7?δ (Y-123) bulk superconductors with the addition of (0.0, 0.2, 0.4, 0.6, 0.8, and 1.0 wt.%) SnO2 nanoparticles were synthesised via a thermal treatment method. The in?uence of SnO2 addition on the superconducting properties by means of critical temperature, Tc, AC susceptibility, phase formation and microstructures, including its elemental composition analysis, were studied. Sharp superconducting transition, ?Tc, and diamagnetic transition were obtained for all SnO2-added samples. It was observed that sample x = 0.4 with a Y-123 phase percentage of 95.8% gives the highest Tc, smallest ?Tc, and the sharpest diamagnetic transition in the normalised susceptibility curves. The microstructure also showed an excess of Sn precipitates on the sample’s surface at x = 0.8 and above. As such, the best superconducting properties were observed at x = 0.4 SnO2 addition inside the Y-123 host sample.
关键词： YBa2Cu3O7?δ,bulk superconductor,additions,SnO2,thermal treatment method
更新于2025-09-23 15:23:52
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Improvement of the critical temperature of NbTiN films on III-nitride substrates
摘要： In this paper, we study the impact of using III-nitride semiconductors (GaN, AlN) as substrates for ultrathin (11 nm) superconducting films of NbTiN deposited by reactive magnetron sputtering. The resulting NbTiN layers are (111)-oriented, fully relaxed, and they keep an epitaxial relation with the substrate. The higher critical superconducting temperature (Tc = 11.8 K) was obtained on AlN-on-sapphire, which was the substrate with smaller lattice mismatch with NbTiN. We attribute this improvement to a reduction of the NbTiN roughness, which appears associated to the relaxation of the lattice misfit with the substrate. On AlN-on-sapphire, superconducting nanowire single photon detectors (SNSPDs) were fabricated and tested, obtaining external quantum efficiencies that are in excellent agreement with theoretical calculations.
关键词： single photon detector,superconductor,NbTiN,AlN,GaN
更新于2025-09-23 15:23:52
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High-<formula><tex>$T_\rm{c}$</tex></formula> Superconducting Fourth-Harmonic Mixer using a Dual-Band Terahertz On-Chip Antenna of High Coupling Efficiency
摘要： This paper presents a dual-band on-chip antenna coupled high-Tc superconducting (HTS) Josephson-junction sub-terahertz (THz) fourth-harmonic mixer. The antenna utilizes a couple of different structured twin-slots to enable the resonant radiations at two frequencies, and integrates a well-designed coplanar waveguide (CPW) network for achieving good radiation coupling and signal isolation characteristics. The electromagnetic (EM) simulations show that coupling efficiencies as high as -4 dB and -3.5 dB are achieved for the 160-GHz and 640-GHz operating frequency bands, respectively. Based on this dual-band antenna, a 640-GHz HTS fourth-harmonic mixer is developed and characterized in a range of operating temperatures. The mixer exhibits a measured conversion gain of around -18 dB at 20 K and -22 dB at 40 K respectively. The achieved intermediate-frequency (IF) bandwidth is larger than 23 GHz. These are the best results reported for HTS harmonic mixers at comparable sub-THz frequency bands to date.
关键词： high-temperature superconductor Josephson junction,dual-band on-chip antenna,terahertz wireless applications,fourth-harmonic mixing,Terahertz mixer
更新于2025-09-23 15:23:52
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Microstructural Aspects of Infiltration Growth YBCO Bulks with Chemical Pinning
摘要： Single grain YBa2Cu3O7-x (YBCO, Y123) bulk superconductors were prepared by infiltration growth (IG) process. The solid phase precursor was prepared by solid state synthesis from Y2O3+BaCuO2 powders. The influence of the composition of the source of melt for infiltration and the CeO2 addition on the transition temperature and critical current density was studied. It is shown that the studied samples are doped by Yb from the Yb2O3 substrate. The dependences of Yb concentration on the distance from the bottom of the samples were measured by EDS microanalysis at SEM. Correlation between the fabrication technology, level of Yb doping, microstructure and superconducting properties is discussed.
关键词： infiltration growth,chemical pinning,microstructure,YBCO bulk superconductor
更新于2025-09-23 15:22:29
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Superconducting one-dimensional photonic crystal with coupled semiconductor defects
摘要： We investigate the impact of the insertion of a semiconductor defect on the transmittance spectrum of a one-dimensional photonic crystal composed by alternating layers of superconducting materials. We report that the effect of the insertion of the semiconductor defect originates a defective mode in the photonic band gap that exhibits a shift towards long-wavelength regimes. Unexpectedly, for high values of temperatures, it is observed that the defective mode reduces its confinement as well as influences the optical response of the photonic crystal rather than the pressure. We also extend our analysis to the case of two coupled defects of GaAs, and it is studied the effect of the relative distance between these two defects. Our numerical results reveal that the defective mode has a significant reduction in its quality factor as well as it displays an asymmetry in the transmittance spectrum when the defects are close to each other.
关键词： Transfer matrix method,Defect mode,Semiconductor,Transmittance spectrum,One-dimensional photonic crystal,Superconductor
更新于2025-09-23 15:21:01
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Photoresponse of current-biased superconductor/normal metal strip with large ratio of resistivities
摘要： Detection of electromagnetic radiation by superconductor is based on destruction of superconductivity by photons and corresponding change of resistance of superconducting sample. For example in the superconducting bolometer or transition edge sensor (TES) the superconductor is biased near the resistive transition, at temperature below the critical temperature Tc of superconductor [1, 2]. The absorbed photons heat up electrons in the detector, electron temperature increases and it leads to the increase of the temperature dependent resistance of superconductor R(T ). In such a detector the sharper the dependence R(T ) the higher sensitivity the superconducting detector has.
关键词： single photon counting,bolometric regime,photoresponse,superconductor,normal metal
更新于2025-09-23 15:21:01
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Clustered atom-replaced structure in single-crystal-like metal oxide
摘要： By means of metal organic deposition using tri?uoroacetates (TFA-MOD), we replaced and localized two or more atoms in a single-crystalline structure having almost perfect orientation. Thus, we created a new functional structure, namely, clustered atom-replaced structure (CARS), having single-crystal-like metal oxide. We replaced metals in the oxide with Sm and Lu and localized them. Energy dispersive x-ray spectroscopy results, where the Sm signal increases with the Lu signal in the single-crystalline structure, con?rm evidence of CARS. We also form other CARS with three additional metals, including Pr. The valence number of Pr might change from 3+ to approximately 4+, thereby reducing the Pr–Ba distance. We directly observed the structure by a high-angle annular dark-?eld image, which provided further evidence of CARS. The key to establishing CARS is an equilibrium chemical reaction and a combination of additional larger and smaller unit cells to matrix cells. We made a new functional metal oxide with CARS and expect to realize CARS in other metal oxide structures in the future by using the above-mentioned process.
关键词： superconductor,YBCO,quasi-liquid network model,clustered atom-replaced structure,cluster,TFA-MOD
更新于2025-09-23 15:21:01
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The Optical Properties of Metamaterial-Superconductor Photonic Band Gap With/Without Defect Layer
摘要： In the present work, we have investigated theoretically the optical properties of a new one-dimensional defected photonic crystal structure (1DDPC). The structure is composed of alternating layers of metamaterial (double-negative material) and high Tc superconductor material called Hg1223 defected with a dielectric material (SiO2) at the center of the structure. The transmittance spectra of the proposed structure are obtained by using the transfer matrix method (TMM). We noticed that multiple transmittance peaks within the photonic band gap (PBG) as the thickness of defect layer increases. The tunable filtering feature is obtained by varying the thicknesses of metamaterial and superconductor layer. In addition, the defect peak is red shifted as well as photonic band gap tuned to low-frequency region. Our structure is sensitive to the variation of the angle incidence. Also, defect mode shown to be blue shifted as the angle of incidence increases. The tunable filtering properties are very useful in the optoelectronic applications.
关键词： Metamaterial,Photonic band gap,TMM,Superconductor
更新于2025-09-23 15:21:01