Polarization switching mechanism in HfO₂ from first-principles lattice mode analysis

Ferroelectricity in HfO₂ can even sustain in thin films, making HfO₂ based materials of intense research interest. The antipolar and polar modes in the ferroelectric phase couple through trilinear terms, making the polarization switch path complex and non-unique. In this work, we carry out first-principles calculations and lattice modes analysis to systematically investigate the polarization switching mechanism in HfO₂. We demonstrate that distortion of cubic HfO₂ leads to several competing variants and complex electric-field switching. We identify the most favorable switching paths by investigating the polar-nonpolar mode coupling and show that switching is only possible to particular variants with the same sign in the X₂^- mode. The implication of the results for interpreting recent experimental observations in HfO₂ based materials and other ferroelectrics with complex lattice mode coupling will also be discussed.