A first-principles study of ferroelectricity via symmetry-mode couplings

Abstract

Polarization—the net dipole moment per unit volume—is the fundamental response of insulating materials to an external electric field. Ferroelectrics are a unique class of insulators capable of sustaining spontaneous polarization even in the absence of an applied field. Since their discovery nearly a century ago, our understanding of ferroelectrics has rapidly advanced, driving significant technological innovations. However, recent findings suggest that ferroelectricity still harbors unexplored phenomena with the potential to revolutionize future applications. In this dissertation, I present the core body of research conducted during my graduate studies, beginning with first-principles simulations of polarization switching in ferroelectrics using density functional theory, combined with group theory and the Landau-Ginzburg-Devonshire theory. I then explore an emerging application of ferroelectric-supported catalysis. Specifically, I present a method to examine how polarization switching modulates adsorption and reaction processes in dynamic catalysis. Next, I investigate the competitive coupling between octahedral rotations and polarization in perovskites, which can give rise to antiferroelectric behavior. Finally, I introduce the concept of "hybrid-triggered" ferroelectricity, arising from unconventional phonon couplings. This discovery gives rise to the concept of higher-order dynamical charges, which may provide a key mechanism underlying the mitigation of one of the most significant barriers to the technological deployment of ferroelectrics: the depolarization field in the thin-film limit.