The optical permittivity of monocrystalline direct bandgap semiconductors can be described well by critical point models based on parabolic band approximation (CPPB). However, the optical permittivity of polycrystalline direct bandgap semiconductors like halide perovskite thin films requires a more precise description. Till now, only thermal bandgap fluctuation or exponential decay of density of states is incorporated into the CPPB model. We present an analytical calculation that is based on the CPPB model with only one additional physical assumption, namely, the Gaussian distributed bandgap energies (GCPPB). Furthermore, the GCPPB model satisfies the Kramers-Kronig causality relation.
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http://dx.doi.org/10.1364/OL.542250 | DOI Listing |
The ability to significantly enhance near-field coupling between light and matter at the nanoscale is crucial for advancing the fields of nanophotonics and nanopolariotonics. However, conventional probes face challenges in achieving optimal light-matter interaction. In this study, we propose a novel, to the best of our knowledge, simulation-based strategy that leverages tip engineering to dramatically amplify the scattering field through tailored double-layer geometries.
View Article and Find Full Text PDFThe optical permittivity of monocrystalline direct bandgap semiconductors can be described well by critical point models based on parabolic band approximation (CPPB). However, the optical permittivity of polycrystalline direct bandgap semiconductors like halide perovskite thin films requires a more precise description. Till now, only thermal bandgap fluctuation or exponential decay of density of states is incorporated into the CPPB model.
View Article and Find Full Text PDFACS Nano
January 2025
Department of Physics, The University of Tokyo, Bunkyo, Tokyo 113-0033, Japan.
We have found that surface superstructures made of "monolayer alloys" of Tl and Pb on Si(111), having giant Rashba effect, produce nonreciprocal spin-polarized photocurrent via circular photogalvanic effect (CPGE) by obliquely shining circularly polarized near-infrared (IR) light. CPGE is here caused by the injection of in-plane spin into spin-split surface-state bands, which is observed only on Tl-Pb alloy layers but not on single-element Tl nor Pb layers. In the Tl-Pb monolayer alloys, despite their monatomic thickness, the magnitude of CPGE is comparable to or even larger than the cases of many other spin-split thin-film materials.
View Article and Find Full Text PDFAppl Spectrosc
December 2024
School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing, China.
The optical and dielectric properties of opals with different water contents were investigated using terahertz time-domain spectroscopy. The refractive indices and absorption coefficients showed different trends due to the different water contents. The effective medium theory was used to extract the intrinsic dielectric permittivity of opal from opal-polytetrafluoroethylene mixtures.
View Article and Find Full Text PDFHeliyon
December 2024
Department of Glass & Ceramic Engineering, Rajshahi University of Engineering & Technology (RUET), Rajshahi-6204, Bangladesh.
This study explored the structural, optical, antibacterial, and dielectric properties of TiO nanoparticles synthesized using two distinct approaches: sol-gel and biosynthesis. Density functional tight binding (DFTB+) and density functional theory (DFT) calculations were employed alongside experimental techniques to gain a comprehensive understanding of the electronic-property relationships. peel extract was utilized for the biosynthesis method.
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