Enhanced transient negative capacitance during inhomogeneous ferroelectric switching

The reversal of polarization in a ferroelectric material involves overcoming an energy barrier, and has been previously proposed and found to yield transient negative capacitance (NC) in the intermediate states of the switching process. Homogeneous switching was assumed to interpret the experimental results of NC; however, inhomogeneous switching is a more abundant mechanism than homogeneous switching, but its possible effect on NC is basically unknown. Here, we use first-principles-based techniques to investigate the occurrence of NC during these two types of switching processes in the supertetragonal phase of ${\mathrm{BiFeO}}_{3}$. We find NC in both cases, but with the magnitude of the inverse of the capacitance being drastically larger in the inhomogeneous (nucleation limited) switching, as compared to the homogeneous switching. We further analyze the origin of the different NC effects, and point to the different energetic trajectories between these two representative switching mechanisms.