Existence of switchable ferroelectric order in tetragonal hybrid perovskites

Establish whether tetragonal hybrid lead-halide perovskites possess strong, switchable macroscopic ferroelectric order rather than merely ferroelasticity or local inversion-symmetry breaking.

Background

Ferroelasticity is established in the relevant materials, but evidence for switchable ferroelectricity is complicated by small candidate polar distortions, molecular-cation disorder, and ionic conduction that can mimic hysteresis. The review therefore treats the existence of macroscopic switchable polarization as unresolved.