Unveiling CsInTiO₄ quantum dots: A novel wide-band-gap material with exceptional nonlinear optical properties

Abstract

A comprehensive detailed theoretical investigation into structural, optical, and optoelectronic properties of _caesium indium titanate (CsInTiO₄) quantum dots (QDs), modelled with a unit cell size of approximately 15 Å. As a structural analogy of CsAlTiO₄, CsInTiO₄ crystallizes in a monoclinic phase with space group $(P21/N)$, as confirmed by X-ray diffraction (XRD) analysis. The material exhibits a wide optical band gap $\left(5.33\mathrm{eV}\right)$, classifying it as a robust wide-band-gap insulator. Optical dispersion behavior was analyzed using the Wemple-DiDomenico model, yielding a high single-oscillator energy ($E₀=7.68\mathrm{eV}$) and oscillator strength of ($f=35.8\mathrm{eV²}$), indicative of strong ionic character and electronic stability. Furthermore, nonlinear optical (NLO) characterization revealed a significant third-order susceptibility (${\chi }^{\left(3\right)}$) and a high nonlinear refractive index ($n_2$), highlighting the material’s strong nonlinear response. Such insights, supported by both theoretical simulations and XRD data, represent the 1st detailed exploration of CsInTiO₄-QDs, laying the ground for upcoming experiments. These numerical benchmarks not only establish CsInTiO₄-QDs as a wide-band-gap insulator but also underscore their exceptional potential for UV optoelectronic and nonlinear optical applications.