We derive a numerical method based on coupled density functional theory and effective Hamiltonian schemes to calculate the linear and quadratic electro-optic response of ferroelectrics at finite temperature and in different frequency ranges. By applying the developed method to BaTiO_{3}, we successfully resolve apparent discrepancies in the experimental literature that reported a linear or quadratic electro-optic response when visible or terahertz radiation was employed to measure the optical index, respectively. We further demonstrate that (and explain why), in the case of the Ba_{1-x}Sr_{x}TiO_{3} disordered solid solutions, structural phase transitions not only lead to larger linear electro-optic constants, as previously demonstrated in the literature, but also significantly enhance the quadratic electro-optic constants.
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http://dx.doi.org/10.1103/PhysRevLett.132.196901 | DOI Listing |
Sci Rep
December 2024
Department of physics, Faculty of Science, Malayer University, Malayer, Iran.
This study investigates the optical properties of carbon nanotubes (CNTs) and silicene nanotubes (SiNTs) under the influence of external magnetic fields, focusing on their linear and nonlinear optical responses. A tight-binding model is employed to analyze the effects of magnetic fields on the electronic band structure, dipole matrix elements, and various optical susceptibilities of zigzag CNTs and SiNTs. The results reveal significant magnetic field-induced modifications in both linear and nonlinear optical spectra.
View Article and Find Full Text PDFPhys Chem Chem Phys
August 2024
Laboratoire de Physique des Matériaux, Faculté des Sciences de Bizerte, Université de Carthage, 7021 Zarzouna, Tunisia.
In this paper, we undertake a theoretical investigation into the effects of both in-plane and out-of-plane static electric fields on moiré interlayer excitons (IXs) within a WSe/MoSe heterobilayer. We thoroughly analyze a wide range of properties pertaining to the IXs, including the binding energy, Stark shift, orbital hybridization, photoluminescence (PL) spectra, and radiative lifetime. Various factors influencing IX behavior, such as the dielectric environment, spacing separation, and moiré trap effects, are examined in detail.
View Article and Find Full Text PDFRev Sci Instrum
July 2024
Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.
Potassium tantalate niobate (KTa1-xNbxO3, KTN) single crystals have a very large relative permittivity εr (>104) just above the paraelectric to ferroelectric phase transition temperature (TC). The quadratic electro-optic coefficient and the electro-strictive coefficient are also very large because of their proportionality to εr2. However, the local relative permittivity can easily vary spatially due to the incongruently melting nature of KTN.
View Article and Find Full Text PDFPhys Rev Lett
May 2024
Smart Functional Materials Center, Department of Physics and Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, Arkansas 72701, USA.
We derive a numerical method based on coupled density functional theory and effective Hamiltonian schemes to calculate the linear and quadratic electro-optic response of ferroelectrics at finite temperature and in different frequency ranges. By applying the developed method to BaTiO_{3}, we successfully resolve apparent discrepancies in the experimental literature that reported a linear or quadratic electro-optic response when visible or terahertz radiation was employed to measure the optical index, respectively. We further demonstrate that (and explain why), in the case of the Ba_{1-x}Sr_{x}TiO_{3} disordered solid solutions, structural phase transitions not only lead to larger linear electro-optic constants, as previously demonstrated in the literature, but also significantly enhance the quadratic electro-optic constants.
View Article and Find Full Text PDFAdv Mater
April 2024
Department of Chemistry, City University of Hong Kong, Hong Kong SAR, 999077, China.
Harnessing the quadratic electro-optic (QEO) of near-infrared polymethine chromophores over broad telecom wavelength bands is a subject of immense potential but remains largely under-investigated. Herein a series of push-pull heptamethines containing the tricyanofuran (TCF) acceptors and indoline or benzo[e]indoline donors are reported. These dipolar chromophores can attain a highly delocalized "cyanine-like" electronic ground state in solvents spanning a wide range of polarities, in some cases even closer to the ideal polymethine state than symmetrical cyanines.
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