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.

中文翻译：

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BaTiO3 中高频极化切换的限制


在这项工作中，我们使用分子动力学模拟来研究 BaTiO3 铁电体在高振幅高频振荡电场作用下的开关行为。虽然在较低频率下，我们观察到标准的方形磁滞回线行为，但在接近 1 THz 的频率下，磁滞回线呈椭球形。随着频率的增加，平均极化振荡而不切换方向。为了阐明偏振切换的 ∼1 THz 极限的来源，我们分析了晶胞级偏振矢量图。在这种情况下，对低频开关事件的分析表明，除了大多数表现出快速开关的偏振矢量外，一些“亚稳态”对齐的偏振矢量持续时间更长，平均寿命为 ∼1 ps。当频率增加到太赫兹范围时，多条偏振矢量线保持未切换状态，从而阻止了仿真域级别的偏振切换。此外，我们观察到，随着外加电场振幅的增加，可以增加观察到开关的频率。