On the structure of the microscopic dielectric tensor in incommensurate crystals

• Published in: Phase transitions Vol. 72; no. 3; pp. 157 - 164
• Main Authors: Kushnir, O. S., Lokot, L. O.
• Format: Journal Article
• Language: English
• Published: Reading Taylor & Francis Group 01-01-2000; Taylor and Francis
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectric permittivity tensor; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Incommensurate phase; Insulator; Microscopic theory; Optical constants (including refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity); Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Physics; Specific phase transitions; Tensors; Incommensurate phases; Phase transformations; Optical properties; Insulating materials; Theoretical study; Microscopic model; Permittivity
• ISSN: 0141-1594; 1029-0338
• DOI: 10.1080/01411590008228987

A microscopic model for calculating the optical response of incommensurately modulated phases in insulating crystals is presented. The dominant contribution to the dielectric permittivity tensor is shown to originate from the lowest-index reciprocal lattice vectors, thus proving the validity of the mesoscopic approach developed in several earlier studies. The expression for the mesoscopic Fourier component of the dielectric tensor is obtained. These results may be useful in relation to the controversial problem of the optical activity observed in the incommensurate phases of some A
2
BX
4
family crystals.