Crossover from Linear to Quadratic Electro-optic Behavior in BaTiO_{3} and (Ba, Sr)TiO_{3} Solid Solution

Area of Science:

• Condensed matter physics
• Materials science
• Computational physics

Background:

• Ferroelectric materials exhibit significant electro-optic effects, crucial for optical device applications.
• Experimental studies on the electro-optic response of ferroelectrics like BaTiO3 have yielded conflicting results.
• Understanding the temperature and frequency dependence of these responses is vital for material design.

Purpose of the Study:

• To develop a robust numerical method for calculating linear and quadratic electro-optic responses of ferroelectrics.
• To resolve discrepancies in experimental data for BaTiO3.
• To investigate the impact of structural phase transitions on electro-optic properties in Ba1-xSrxTiO3 solid solutions.

Main Methods:

• Coupled density functional theory (DFT) and effective Hamiltonian schemes were employed for calculations.
• The method accounts for finite temperature effects and various frequency ranges.
• The approach was validated using barium titanate (BaTiO3) and barium strontium titanate (Ba1-xSrxTiO3) systems.

Main Results:

• The numerical method successfully reproduced experimental observations for BaTiO3, resolving previous inconsistencies.
• The study demonstrated that structural phase transitions in Ba1-xSrxTiO3 significantly enhance both linear and quadratic electro-optic constants.
• The underlying physical mechanisms for these enhancements were elucidated.

Conclusions:

• The developed computational method provides a reliable tool for predicting electro-optic properties of ferroelectrics.
• The findings clarify the behavior of BaTiO3 under different experimental conditions.
• This work offers insights into optimizing ferroelectric materials for advanced electro-optic applications through controlled structural modifications.