Topological ferroelectric phases by mode-selective phonon excitation

Abstract

Topological structural phases (TSPs) of nontrivial winding numbers are of long-standing fundamental relevance in the theory of phase transition. However, for decades, no TSPs have been discovered in technological ferroelectric bulk solids. Here we formulate a generally applicable scheme to create TSPs in ferroelectrics. The approach consists in selectively exciting phonon modes to produce the targeted TSPs and can be employed to generate TSPs that do not naturally exist in bulk materials. We further demonstrate the effectiveness of this approach by creating in bulk ${\mathrm{SrTiO}}_{3}$ three TSP structures, namely the flower phase, the tetragonal-like vortex phase, and the orthorhombiclike vortex phase. These topological phases lead to the discovery of interesting properties, which include (i) a marked difference in the excitation stiffness of different topological phases and (ii) the existence of symmetry breaking between vortex phases.