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Extreme Huygens' metasurfaces based on quasi-bound states in the continuum
摘要： We introduce the concept and a generic approach to realize Extreme Huygens’ Metasurfaces by bridging the concepts of Huygens’ conditions and optical bound states in the continuum. This novel paradigm allows creating Huygens’ metasurfaces whose quality factors can be tuned over orders of magnitudes, generating extremely dispersive phase modulation. We validate this concept with a proof-of-concept experiment at the near-infrared wavelengths, demonstrating all-dielectric Huygens’ metasurfaces with different quality factors. Our study points out a practical route for controlling the radiative decay rate while maintaining the Huygens’ condition, complementing existing Huygens’ metasurfaces whose bandwidths are relatively broad and complicated to tune. This novel feature can provide new insight for various applications, including optical sensing, dispersion engineering and pulse-shaping, tunable metasurfaces, meta-devices with high spectral selectivity, and nonlinear meta-optics.
关键词： all-dielectric,dispersion,bound states in the continuum,Huygens’ condition,metasurfaces
更新于2025-09-23 15:21:21
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A Restricted Quantum Deniable Authentication Protocol Based on GHZ States
摘要： Utilizing the property of unitary transformation and Greenberger-Horne-Zeilinger (GHZ) states, a restricted quantum deniable authentication protocol is proposed. The protocol can provide that the sender can deny the content of the sent message, but cannot deny taking part in a certain communication. Security analysis results show that this protocol can satisfy known key security and the basic security requirements of restricted deniable authentication protocol such as completeness, restricted deniability, no-counterfeiting and can withstand impersonation attack, intercept-resend attack.
关键词： Quantum deniable authentication,Restricted,Greenberger-Horne-Zeilinger (GHZ) states
更新于2025-09-23 15:21:21
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[Springer Series in Optical Sciences] Fano Resonances in Optics and Microwaves Volume 219 (Physics and Applications) || Study of Fano Resonance in the Core-Level Absorption Spectrum in Terms of Complex Spectral Analysis
摘要： We study theoretically the core absorption spectrum of an impurity embedded in a tight-binding chain in terms of complex spectral analysis. The absorption spectral pro?le associated with the resonance states in principle exhibits an asymmetric Fano-type structure, even without apparent multiple interference transition paths. The asymmetric Fano absorption pro?le is attributed to the complex-valued oscillator strength of the transition to the resonance state belonging to the extended Hilbert space. The boundary condition on the continuum causes a large energy dependence of the self-energy, so that it enhances the nonlinearity of the eigenvalue problem of the effective Hamiltonian, yielding several non-analytic resonance states. The optical transitions to these resonance states constitute the overall absorption spectrum structure.
关键词： Fano resonance,core-level absorption spectrum,complex spectral analysis,extended Hilbert space,resonance states
更新于2025-09-23 15:21:21
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Reflection coefficient of HfO <sub/>2</sub> -based RRAM in different resistance states
摘要： Impedance spectra of multiple resistive states in a stable-switching Resistive Random-Access Memory device based on a stack of Ru/HfO2/Zr/W was studied in this work. Using these observations, re?ection-coef?cients were extracted for different resistive states. Clear changes in the re?ection coef?cient for different resistive states were observed. The device in a low resistive state showed a signi?cantly higher re?ection coef?cient compared to its high resistive state. An increasing trend in the re?ection coef?cient was observed as the device state was gradually recon?gured towards lower resistances. Maximum frequency for re?ection increased with the decrease in the device area. The physics behind this observation is attributed to the interplay of oxygen ion transport among the interfacial layer, conductive ?lament, and HfO2-?lm.
关键词： resistive states,impedance spectra,HfO2,RRAM,reflection coefficient
更新于2025-09-23 15:21:21
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Exploring the potential of iron to replace ruthenium in photosensitizers: a computational study
摘要： In an effort to replace the widely used ruthenium metal complexes with low-cost, earth abundant iron complexes as photosensitizers for dye-sensitized solar cell (DSSC) applications, herein we report the computational design of heteroleptic iron complexes (FC1–3) coordinated with benzimidazole-phenylcarbene (C^N) ligands. DFT and TDDFT calculations predicted the stronger σ-donating and π-accepting nature of phenyl carbene ligands substituted with electron-withdrawing CF3, donating –N(CH3)2, and benzothiazine annulation than the imidazole carbene ligands (FC4); consequently, the metal-ligand bond distances and interactions that influence the ordering of charge transfer states with respect to metal centered states are altered in FC1–3 complexes. Detailed analysis based on energy decomposition analysis, spin density distribution analysis, and ab initio ligand field theory parameters were enabled to understand the nature of heteroleptic ligand interactions with the rest of the metal complex. The results from the study shed light on the judicious choice of ligands, as the same non-innocent ligand that is experimentally proven as favorable for Ru-dyes (TC1) is found to be detrimental for Fe-dyes (FC1). Among the complexes studied, the FC3 complex is a promising sensitizer for DSSC with 1,3MLCT energy level well separated from 3,5MC, thereby preventing the deactivation of MLCT. The outcome of the study is therefore an important step toward the development of photosensitizers based on iron metal.
关键词： DSSC,Photosensitizers,Iron,Spin states,TD-DFT,Carbene ligands,Ruthenium
更新于2025-09-23 15:21:21
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Macroscopic effects and microscopic origins of gamma-ray irradiation on In-doped CdZnTe crystal
摘要： The effects of gamma-ray irradiation, exposed to a 60Co source with a dose of 2.7 kGy, on In-doped CdZnTe (CdZnTe:In) crystal were investigated. We combined the “macroscopic” electrical properties of CdZnTe:In sample, evaluated by current–voltage (I–V) measurements at different temperature, with the “microscopic” origins of electrically active defects induced by gamma-irradiation, characterized by thermally stimulated current spectroscopy. It reveals that the bulk resistivity at room temperature have increased from 2.7 × 109 ? cm for the as-grown CdZnTe:In sample to 5.9 × 109 ? cm for the irradiated sample. Since the microscopic origins of these macroscopic effects are linked to the electrically active defects within the material, five main defect states (I, II, III, IV and V) were characterized and identified in the CdZnTe:In crystal. In particular, the introduction of gamma-irradiation altered the trap concentrations of these defect states, such as the rapidly decreasing concentration of region I. Besides, the gamma-ray irradiation caused a further deepening of EDD level (region V) from the value of 0.717 ± 0.004 eV for the as-grown sample to the value of 0.749 ± 0.004 eV for the irradiated sample. The microscopic origin of EDD level was identified with TeCd2+ below the conduction band minimum, which is responsible for the pinning of EF level near the mid-gap, and thus for the observed high-resistivity performance of CdZnTe:In.
关键词： high-resistivity,electrical properties,defect states,gamma-ray irradiation,CdZnTe:In
更新于2025-09-23 15:21:21
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The effect of alternating current on the current states of a quantum interferometer shunted by a superconducting inductance
摘要： The patterns of reversible changes in the critical current and discrete current states of a structure in the form of a superconducting quantum interferometer shunted by superconducting inductance, as a result of passing an alternating transport current through the structure and applying an external alternating magnetic field simultaneously with a direct transport current, was established. A new type of discrete stationary state was discovered during the transition of the interferometer to the resistive state caused by the combined action of direct and alternating transport currents.
关键词： resistive state,superconducting inductance,alternating current,superconducting quantum interferometer,discrete current states
更新于2025-09-23 15:21:21
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Numerical analysis of surface and edge states in slabs, stripes, rods and surface steps of topological insulators
摘要： By numerically solving the e?ective continuous model of a topological insulator with parameters corresponding to the band structure of the topological insulator Bi2Se3, we analyze possible appearance of one-dimensional states in various geometries. Massless Dirac fermions are found at the edges of thin ribbons with surface oriented not only along the van der Waals gap but also in the perpendicular direction. Thick rods and slabs with surface steps host massive modes localized on surface faces. We argue that the modes are massive and their origin is due to the di?erence in the Dirac point energy of adjacent faces. The absence of one-dimensional states near edges of a large rectangular rod and surface steps is demonstrated.
关键词： bound state,topological insulator,edge states,surface step
更新于2025-09-23 15:21:21
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Quantum Hall phase and chiral edge states simulated by a coupled dipole method
摘要： We present theoretical modeling of the quantum Hall phase and chiral edge states in a gyroelectric photonic crystal. The theoretical framework represented here is based on a coupled dipole method, which is a direct counterpart of the tight-binding approximation. We con?rm that gyrotropic coupling produces a band gap characterized by a nonzero Chern number. Gapless edge states appear at an interface between a gyroeletric photonic crystal and a vacuum. At a domain wall between media of positive and negative gyrotropy, topological edge states that are analogous to the Jackiw-Rebbi states are observed. Propagation of the chiral edge states is also simulated in real space under excitation of an external dipole source. This analysis provides a toy model to describe the quantum Hall phase in a purely optical manner, without using a mapping or an analogy of the electron wave function in the quantum Hall effect.
关键词： quantum Hall phase,chiral edge states,coupled dipole method,topological edge states,gyroelectric photonic crystal
更新于2025-09-23 15:21:01
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Unveiling the radiative local density of optical states of a plasmonic nanocavity by STM
摘要： Atomically-sharp tips in close proximity of metal surfaces create plasmonic nanocavities supporting both radiative (bright) and non-radiative (dark) localized surface plasmon modes. Disentangling their respective contributions to the total density of optical states remains a challenge. Electroluminescence due to tunnelling through the tip-substrate gap could allow the identification of the radiative component, but this information is inherently convoluted with that of the electronic structure of the system. In this work, we present a fully experimental procedure to eliminate the electronic-structure factors from the scanning tunnelling microscope luminescence spectra by confronting them with spectroscopic information extracted from elastic current measurements. Comparison against electromagnetic calculations demonstrates that this procedure allows the characterization of the meV shifts experienced by the nanocavity plasmonic modes under atomic-scale gap size changes. Therefore, the method gives access to the frequency-dependent radiative Purcell enhancement that a microscopic light emitter would undergo when placed at such nanocavity.
关键词： scanning tunnelling microscope luminescence,plasmonic nanocavities,local density of optical states,radiative Purcell enhancement
更新于2025-09-23 15:21:01