We present a comparative experimental and theoretical investigation of the two–dimensional charge-transfer gap in the strongly correlated material Sr2CuO2Cl2. We observe an Urbach behaviour in the absorption profile over a surprisingly wide range of energies and temperatures. We present a model that accounts for phonon scattering to infinite order and which allows us to explain the data accurat...

A 10-year-old girl born of consanguineous marriage presented with hoarseness of voice and difficulty in protruding tongue since last five years. No other family member was affected. Cardiovascular, ophthalmological and neurological examination was normal. Hematological profile was normal, including X-ray skull. Cutaneous examination showed classical multiple beaded papules along the eyelid marg...

Abstract We propose new optical dispersion models to describe the imaginary part of electrical permittivity dielectric and semiconductor materials in fundamental absorption region. work out our procedure based on well-known structure semi-empirical Tauc–Lorentz model band-fluctuations approach derive a five-parameter formula that describes Urbach, Tauc high-absorption regions direct indirect se...

Amorphous semiconductors are materials with a brilliant prospect for a wide range of optical applications like solar cells, optical sensors, optical devices, and memories. The purpose of the present research was to study the semiconducting optical properties of SiO2-Al2O3-CaF2 and SiO2-Al2O3-BaF2 oxyfluoride...

The Tauc–Lorentz–Urbach (TLU) dispersion model allows us to build a dielectric function from only few parameters. However, this is non-analytic and presents some mathematical drawbacks. As consequence of issue, the becomes inaccurate. In present work, we will adopt procedure conveniently transform TLU into self-consistent model. transformation involves integration original imaginary ϵ2 by using...

We present density-functional theory calculations of the optical absorption spectra of silica glass for temperatures up to 2400 K. The calculated spectra exhibit exponential tails near the fundamental absorption edge that follow the Urbach rule in good agreement with experiments. We discuss the accuracy of our results by comparing to hybrid exchange correlation functionals. We show that the Urb...