FEAST - FerroElectricity using Ab-initio Simulations in the Time domain

通过外场控制铁电体的偶极矩代表了基础物理学的挑战以及支撑可能的铁电随机存取存储器器件的关键要求。可以操纵物质的最终时间极限由光波引起的光激发的时间尺度给出，其量级为阿秒到几飞秒。虽然磁序已经出现了丰富的领域，其中磁序的超快光脉冲控制现在已经很好地建立，但探索铁电体的超快控制的相应系统性努力仍处于起步阶段。在这个项目中，我们将应用含时密度泛函理论（TDDFT）的工具，在铁电材料中的电荷和电流的动力学，以理解和预测其行为的飞秒时间尺度。这种第一原理方法--没有任何拟合参数--已被证明在揭示飞秒磁性领域的超快现象方面非常有用，我们将在这里采用TD-DFT来解决基本问题，例如如何利用瞬态电流信号来推断偶极序的时间演化，以及系统地探索超快铁电性在一系列材料中的物理学，从大块铁电体，如扭曲的钙钛矿，到迅速兴起的2$D材料领域。因此，该提案有望促进对超快铁电性基础物理的理解，以及其在关键介电材料中的实际应用。

Controlling the dipole moment of ferroelectrics by external fields represents both a challenge of fundamental physics as well as a key requirement underpinning possible ferroelectric random access memory devices. The ultimate temporal limit at which matter can be manipulated is given by the time scales of lightwave induced optical excitations, of the order of attoseconds to a few femtoseconds. While for magnetic order a rich field has arisen in which control by ultrafast light pulses of magnetic order is now well established, a corresponding systematic effort exploring the ultrafast control of ferroelectrics remains in its infancy. In this project we will apply the tools of time dependent density functional theory (TDDFT) to the dynamics of the electric charge and current in ferroelectric materials in order to understand and predict their behavior on femtosecond timescales. This first principles approach -- free of any fitting parameters -- has proven to be profoundly useful in unveiling ultrafast phenomena in the field of femtomagnetism, and we will here employ TD-DFT to both address fundamental questions, such as how transient current signals can be employed to infer the temporal evolution in dipole order, as well as to systematically explore the physics of ultrafast ferrolectricity in a range of materials from bulk ferroelectrics, such as the distorted Perovskites, to the rapidly emerging field of $2$D materials. The proposal is therefore expected to advance both understanding of the fundamental physics of ultrafast ferroelectricity, as well as its practical application in key dielectric materials.