  Experimental observations suggest that nominally uncharged, as-grown domain
walls in ferroelectric thin films can be conductive, yet comprehensive
theoretical models to explain this behavior are lacking. Here, Landau theory is
used to evolve an analytical treatment of the anisotropic carrier accumulation
by nominally uncharged domain walls in multiferroic BiFeO3. Strong angular
dependence of the carrier accumulation by 180-degree domain walls originates
from local band bending via angle-dependent electrostriction and flexoelectric
coupling mechanisms. Theoretical results are in qualitative agreement with
experimental data, and provide a Landau-Ginzburg-Devonshire counterpart that is
consistent with recent first principles calculations. These studies suggest
that a significantly more diverse range of domain wall structures could possess
novel electronic properties than previously believed. Similarly, emergent
electronic behaviors at ferroic walls are typically underpinned by multiple
mechanisms, necessitating first-principle studies of corresponding coupling
parameters.
