Limits of high-frequency polarization switching in BaTiO3

In this work, we use molecular dynamics simulations to investigate the switching behavior of BaTiO3 ferroelectric under the application of a high-amplitude high-frequency oscillatory electric field. While at lower frequencies, we observe a standard square-shaped hysteresis loop behavior, at frequencies approaching 1 THz, the hysteresis loop has an ellipsoidal shape. As the frequency increases, the average polarization oscillates without switching direction. To elucidate the origin of the ∼1 THz limit for the polarization switching, we analyzed unit-cell-level polarization vector maps. In this context, the analysis of the low-frequency switching events revealed that in addition to the majority of the polarization vectors exhibiting rapid switching, some “metastable” aligned polarization vectors persist longer with an average lifetime of ∼1 ps. As the frequency increases to the THz range, several polarization vector lines remain unswitched, thus preventing the polarization switching at the simulation domain level. Furthermore, we observe that with the increase in the amplitude of the applied electric field, one can increase the frequency at which switching is observed.