Conceptual

Non-Reciprocal Neutral Ferroelectric Domain Walls in BiFeO3

Ab-initio atomistic evidence that the two parallel, charge-neutral 180-degree domain walls bounding a lamella in the multiferroic BiFeO3 need not be symmetry-equivalent: they can differ in polarization and oxygen-octahedra-tilt profile, thickness, and energy density. Students learn what makes a wall non-reciprocal (irreversible), why a neutral wall can nonetheless be non-reciprocal, and how this asymmetry drives the spontaneous formation of zigzag walls and triangular inverted-polarization domains, identifying the true lowest-energy planar 180-degree wall.