CAREER: Hidden Topological Polar Phases Created by Ultrafast Acoustic Excitation

该奖项支持综合研究，教育和推广活动，以促进对铁电体中具有复杂极化模式的新相的基本理解。铁电体是具有有序极化的材料（由一对相隔很小距离的带相等和相反电荷的磁极组成），可以通过外部磁场进行操纵。铁电体中令人兴奋的研究领域之一是创造非常规的极化模式，例如极涡，其中旋转极化可以诱导奇异的基本现象，并为潜在的器件应用提供新的机会，例如超高密度基于涡旋的存储器。然而，这种复杂的极性相迄今为止仅在少数铁电材料中观察到，并且大多数在材料合成期间自发形成。在这个项目中，PI和他的研究团队将在计算上展示一种全新的方法，用于在铁电材料中按需创建复杂的极性相。这种新方法结合了异质结构设计（将铁电薄膜与不同材料集成）和皮秒（万亿分之一秒）超声脉冲的激发。将开发一个新的计算机模型，以确定材料、薄膜厚度、超声脉冲的持续时间和幅度，以及创建新的复杂极性相所需的其他相关参数，从而为异质结构合成和超快控制实验提供指导。研究活动与教育和推广活动相结合，旨在开发、实施、评估、并为初中和高中科学教育传播一系列侧重于微观层面上看到的材料结构（称为微观结构）的课堂模块。课堂模块将涉及微观结构建模，3D打印和机械性能测试的协同活动。这些模块将由两名中学教师、一家教育软件公司、一名研究生和PI合作开发。这些模块将在涵盖不同学生群体的初中和高中进行测试，根据评估结果进行改进，并通过组织教师研讨会和在教育会议上的演讲，广泛传播到威斯康星州的中学，以便这些模块可以用于吸引和激励数百甚至数千名中学生。技术总结该奖项支持综合研究，教育，和推广活动，以促进对拓扑极性相形成的基本理解（例如，涡旋，skyrmions，merons）。由于强的极化梯度，拓扑极性相可以诱导奇异的基本现象，并为潜在的器件应用开辟新的模式。然而，到目前为止，拓扑极性相只在少数铁电异质结中观察到，并且大多数在平衡条件下形成。超快激发是一种很有前途的方法，以创造长期存在的非平衡隐藏相的物质与紧急功能。本研究的主要目的是通过超快声激励在铁电异质结构中计算产生隐藏的拓扑极性相。为了实现这一目标，PI和他的研究团队将开发一种新的介观模型，该模型可以准确快速地预测注入超快声脉冲后铁电异质结构中出现的应变，极化和电磁波的耦合动力学。该模型将被用来预测和理解在平衡条件下的初始极性相的形成和超快声激发后的最终隐藏极性相。研究活动与教育和推广活动相结合，旨在开发，实施，评估和传播一系列专注于初中和高中科学教育的材料微观结构的课堂模块。课堂模块将涉及微观结构建模，3D打印和机械性能测试的协同活动。这些模块将由两名中学教师、一家教育软件公司、一名研究生和PI合作开发。这些模块将在涵盖不同学生群体的初中和高中进行测试，根据评估结果进行改进，并通过组织教师研讨会和在教育会议上的演讲，广泛传播到威斯康星州的中学，这样，这些模块可以用来吸引和激励成百上千的中学生。这个奖项反映了NSF的法定使命，并被认为是值得的通过使用基金会的知识价值和更广泛的影响审查标准进行评估，

NONTECHNICAL SUMMARYThis award supports integrated research, educational, and outreach activities to advance the fundamental understanding of novel phases with complex polarization patterns in ferroelectrics. Ferroelectrics are materials that have orderly polarization (composed of pairs of equal and oppositely charged poles separated by a tiny distance) that can be manipulated by external fields. One of the exciting research areas in ferroelectrics is creating unconventional patterns of polarization, such as a polar vortex, where the swirling polarization can induce exotic fundamental phenomena and provide new opportunities for potential device applications such as ultrahigh-density vortex-based memory. However, such complex polar phases have so far been observed in only a few ferroelectric materials and mostly form spontaneously during materials synthesis. In this project, the PI and his research team will computationally demonstrate a radically new approach towards an on-demand creation of complex polar phases in ferroelectric materials. This new approach combines heterostructure design (integrating ferroelectric thin films with dissimilar materials) and the excitation by picosecond (one trillionth of a second) ultrasonic pulses. A new computer model will be developed to identify the materials, film thickness, duration and amplitude of the ultrasonic pulse, and other relevant parameters needed for the new complex polar phase creation, thereby providing guidance for both heterostructure synthesis and ultrafast control experiments.The research activities are integrated with educational and outreach activities which aim to develop, implement, assess, and disseminate a series of classroom modules focused on material structures seen at the micro level (called microstructures) for middle school and high school science education. The classroom modules will involve synergistic activities of microstructure modeling, 3D printing, and mechanical properties testing. The modules will be collaboratively developed by two secondary-school teachers, an education software company, a graduate student, and the PI. The modules will be tested in middle and high schools covering diverse student population, improved based on assessment results, and broadly disseminated to secondary schools in Wisconsin by organizing a teachers’ workshop and presentations at an educational conference, such that the modules can be used to engage and inspire hundreds and potentially thousands of secondary school students.TECHNICAL SUMMARYThis award supports integrated research, educational, and outreach activities to advance the fundamental understanding of the formation of topological polar phases (e.g., vortices, skyrmions, merons) in ferroelectrics. Due to the strong gradient of polarization, topological polar phases can induce exotic fundamental phenomena and open new modalities for potential device applications. However, topological polar phases have so far been observed in only a few ferroelectric heterostructures and mostly form under equilibrium conditions. Ultrafast excitation is one promising approach to create long-lived nonequilibrium hidden phases of matter with emergent functionalities. The main objective of this research is to computationally create hidden topological polar phases in ferroelectric heterostructures by ultrafast acoustic excitation. To achieve this, the PI and his research team will develop a new mesoscale model that can accurately and rapidly predict the coupled dynamics of strain, polarization, and electromagnetic waves that will emerge in ferroelectric heterostructures after the injection of an ultrafast acoustic pulse. The model will then be utilized to predict and understand the formation of the initial polar phases under equilibrium condition and the final hidden polar phases upon ultrafast acoustic excitation.The research activities are integrated with educational and outreach activities which aim to develop, implement, assess, and disseminate a series of classroom modules focused on materials microstructures for middle school and high school science education. The classroom modules will involve synergistic activities of microstructure modeling, 3D printing, and mechanical properties testing. The modules will be collaboratively developed by two secondary-school teachers, an education software company, a graduate student, and the PI. The modules will be tested in middle and high schools covering diverse student population, improved based on assessment results, and broadly disseminated to secondary schools in Wisconsin by organizing a teachers’ workshop and presentations at an educational conference, such that the modules can be used to engage and inspire hundreds and potentially thousands of secondary school students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.