Domain Walls in the Electronic Polarization of Silver Bismuthate

Ternary bismuth oxides are a new class of atypical ferroelectric materials whose polar states are primarily induced by electronic charge disproportionation rather than atomic displacement. Silver bismuthates are particularly exciting as ferroelectric semiconductors with low band gaps. Previous research has focused primarily on bulk geometry and electronic structure of thee materials, identifying three structural phases of Ag₂BiO₃ as a function of temperature. Understanding domain wall structures and energetics in this material is now critical to facilitate prediction of polarization and domain switching dynamics for applications in memory and opto-electronics.

Here we present structures of candidate domain walls in Ag₂BiO₃, using ab initio methods to determine the relative energies, structural displacements and charge disproportiations associated with of these domain walls. We also calculate the spatial width of the domain walls, the energy landscape of the polarization order parameter, and the bulk elastic response of the material. These quantities now facilitate phase field simulations of the polarization dynamics in Ag₂BiO₃, providing insight into the domain-switching dynamics from nano to micro scales.