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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 27: Polar oxides: Lithium niobate and lithium tantalate

KFM 27.2: Vortrag

Donnerstag, 21. März 2024, 15:20–15:40, TC 010

Theoretical Modelling of Domains and Domain Walls in Ferroelectric Oxides — •Leonard Verhoff and Simone Sanna — Institut for Theoretical Physics, Justus Liebig University, Giessen, Germany

Ferroelectric domain walls (DW) in lithium niobate (LN) and lithium tantalate (LT), i.e. interfaces between regions of different polarization, present a compelling field of study with diverse emergent functionalities. DW not only exhibit unique electronic and optical properties but also present a rich avenue for tailoring and manipulating the material’s behaviour for advanced applications in optoelectronics and information processing.
We employ various methods to model DW parallel to the z-axis in the ferroelectric oxides LN and LT. Beginning with a symmetry-based description, we utilizie Ginzburg-Landau-Devonshire theory for qualitative insights. We delve into specific, high-symmetry DW orientations through density functional theory (DFT) calculations to investigate the ionic structure around the DW and the respective formation energies in detail. These energies, interpreted as interaction strengths of neighboring domains, are then incorporated into a 2D Ising model to simulate the formation of DW on a larger scale lattice, that would be inaccessible through DFT due to the large number of atoms. Special emphasis is placed on understanding the shape of emerging ferroelectric domains, with a focus on the anisotropy of formation energy that leads to hexagonal domain shapes in LN, while LT forms triangular domains.

Keywords: Domain Walls; Lithium niobate/tantalate; Ising Model; DFT; Ginzburg-Landau-Devonshire Theory