Research suggests a new class of ferroelectric materials

Mandel, Savannah

doi:10.1063/10.0000632

Cited by 1 publication

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“…Adapted with permission from REF. 229 . b | Dipole configurations in four selected areas of a bent membrane by atomistic simulations, featuring a-domains, c-domains and transitional domains.…”

Section: Box 3 | Conduction Mechanismsmentioning

confidence: 99%

Domain-wall engineering and topological defects in ferroelectric and ferroelastic materials

et al. 2020

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Ferroelectric and ferroelastic domain walls are two-dimensional (2D) topological defects with thicknesses approaching the unit cell level. When this spatial confinement is combined with observations of emergent functional properties, such as polarity in non-polar systems or electrical conductivity in otherwise insulating materials, it becomes clear that domain walls represent a new and exciting state of matter. In this review, we discuss the exotic polarisation profiles that can arise at domain walls with multiple order parameters and the different mechanisms that lead to domain wall polarity in non-polar ferroelastic materials. The emergence of energetically degenerate variants of the domain walls themselves suggests the existence of interesting quasi-1D topological defects within such walls. We also provide an overview of the general notions which have been postulated as fundamental mechanisms responsible for domain wall conduction in ferroelectrics. We then discuss the prospect of combining domain walls with transition regions observed at phase boundaries, homo-and heterointerfaces, and other quasi-2D objects, enabling emergent properties beyond those available in today's topological systems. Key points• In ferroelectrics, the emergence of a second polarisation component leads to analogues of Bloch and Néel walls. The stabilization of these walls opens the possibility for quasi-1D topological defects separating wall regions of opposite polarities.• Polar domain walls in ferroelastics rely on two mechanisms: a polarity imposed by the natural symmetry of strain-compatible domain walls, which can often be described by flexoelectric gradient coupling, and the emergence of a potentially switchable polarity when their natural symmetry is broken.• Several mechanisms are responsible for domain wall conduction in ferroelectrics: extrinsic intra-bandgap defect states, intrinsic suppression of the conduction band and intrinsic shift of the band structure induced by local electric fields.• Transition regions occurring at phase boundaries, homo-and heterointerfaces, and other quasi-2D objects probably exist at a smaller length scale, in the vicinity of domain walls, and could lead to exceptional properties and coupling phenomena.

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Section: Box 3 | Conduction Mechanismsmentioning

confidence: 99%