Nonequilibrium Control of Magnetism and Topology Through Selective Phonon Excitations

该奖项支持旨在理解和预测量子材料中物质新体制的研究和教育活动。PI将把他的理论研究重点放在由不同光频率和偏振的激光照射导致的非平衡材料上。激光的高纯度光，与来自太阳或灯泡的光相比，几乎是单一频率，允许人们有选择地将能量沉积到固体材料的不同自由度（例如晶格，电子，磁性）中。因为这些不同的自由度相互作用，沉积在一个自由度中的能量最终会在一段时间后分布到其他自由度中，但在中间时间会产生有趣的非平衡现象。该项目的目标是在理论上揭示有趣的电和磁可能性，并帮助指导实验小组在实验室中实现它们。最终，这项研究可能会实现基于光控制物质的新量子技术，包括传感、计算和通信应用。此外，该项目将通过直接参与PI所描述的研究来支持研究生和本科生的培训。PI将继续提供广泛的公开讲座，重点关注来自历史上代表性不足的背景的大学预科学生，他们对理论物理和/或量子科学的接触有限。其中一些讲座将通过东北大学STEM教育中心进行。PI将参加东北大学的“建立桥梁计划”（Building Bridges Program）和东北大学的“青年学者计划”（Young Scholars Program）。前者是一个互动日，旨在向未来的大学生介绍科学和工程知识。后者是一个为期6周的密集暑期计划，即将毕业的高中生将在该计划中研究前沿研究问题，并接受教师和大学生的指导。技术概述：该奖项支持研究和教育活动，旨在了解和预测量子材料中非平衡物质的新制度。PI将从理论上研究激光诱导晶格变化对具有强自旋轨道耦合的相关电子材料的电子态的影响。该项目将大大扩展具有强自旋轨道耦合和电子相关的系统的平衡研究到非平衡状态。通过光直接瞄准材料中的选定声子模式，可以最小化热效应，并产生相干的电子和磁响应。拓扑转变，包括高阶拓扑状态，在电子和磁振子带结构和布里温区Berry曲率的再分布，以及相变/相稳定的不寻常的电荷有序，磁有序，和超导状态将是一个焦点。特别令人感兴趣的是材料在强光作用下可能产生的非线性效应。非线性声子研究和线性响应机制之外的效应（如高谐波产生）将作为驱动和检测由强低频光产生的新物理机制和激发的手段进行研究。PI将使用互补的理论方法，从强耦合极限和弱耦合状态出发，探索激光诱导晶格变化与电子/磁性能变化之间的联系。数值和分析方法，包括模型哈密顿和第一原理研究，以及对称论证将被采用。此外，该项目将通过直接参与PI所描述的研究来支持研究生和本科生的培训。PI将继续提供广泛的公开讲座，重点关注来自历史上代表性不足的背景的大学预科学生，他们对理论物理和/或量子科学的接触有限。其中一些讲座将通过东北大学STEM教育中心进行。PI将参加东北大学的“架桥计划”（Building Bridges Program）和东北大学的“青年学者计划”（Young Scholars Program）。前者是一个互动日，旨在向未来的大学生介绍科学和工程知识。后者是一个为期六周的密集暑期计划，即将毕业的高中生将在该计划中研究前沿研究问题，并接受教师和大学生的指导。该奖项反映了美国国家科学基金会的法定使命，并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，被认为值得支持。

NONTECHNICAL SUMMARYThis award supports research and educational activities with an aim to understand and predict novel regimes of matter in quantum materials. The PI will focus his theoretical research on materials driven out-of-equilibrium from illumination by lasers of different light frequencies and polarization. The high purity light of a laser, which is very nearly of a single frequency in contrast to light from the sun or a light bulb, allows one to selectively deposit energy into the different (e.g. lattice, electronic, magnetic) degrees of freedom of a solid material. Because these different degrees of freedom interact with one another, energy deposited in one will ultimately be distributed among the others after some time, but at intermediate times interesting non-equilibrium phenomena can result. The goal of this project is to uncover interesting electrical and magnetic possibilities theoretically, and help guide experimental groups in their realization in the laboratory. Ultimately, this research may enable new quantum technologies based on light control of matter, including sensing, computing, and communication applications.In addition, this project will support the training of graduate and undergraduate students through direct involvement with the PI in the research described. The PI will continue to deliver a wide range of public lectures with a focus on pre-college students from historically underrepresented backgrounds who have had limited exposure to theoretical physics and/or quantum sciences. Some of these lectures will be delivered through Northeastern University’s Center for STEM Education. The PI will participate in the Building Bridges Program at Northeastern, an interactive day to introduce prospective college students to the sciences and engineering, and the Young Scholars program at Northeastern, a 6-week intensive summer program where rising high-school seniors work on cutting edge research problems and receive mentoring from faculty and university students.TECHNICAL SUMMARYThis award supports research and educational activities with an aim to understand and predict novel regimes of matter in quantum materials out-of-equilibrium. The PI will theoretically study the influence of laser-induced lattice changes on the electronic states of correlated electronic materials with strong spin-orbit coupling. The project will substantially extend equilibrium studies of systems with both strong spin-orbit coupling and electronic correlations to the non-equilibrium regime. By directly targeting selected phonon modes in a material with light, heating effects can be minimized, and coherent electronic and magnetic responses generated. Topological transitions, including higher order topological states, in the electronic and magnon band structures and redistribution of Berry curvature in the Brillouin zone will be a focus, as well as phase transitions/phase stabilization of unusual charge-ordered, magnetically-ordered, and superconducting states. Of particular interest will be nonlinear effects that may be induced in the materials through intense light. Nonlinear phononic studies and effects beyond the linear response regime (such as higher harmonic generation) will be studied as a means to drive and detect novel physical regimes and excitations created by intense, low-frequency light. The PI will use complementary theoretical methods that start from both the strong coupling limit and the weak coupling regime to explore the link between laser-induced lattice changes and electronic/magnetic property changes. Numerical and analytical approaches, including model Hamiltonian and first-principles studies, along with symmetry arguments will be employed.In addition, this project will support the training of graduate and undergraduate students through direct involvement with the PI in the research described. The PI will continue to deliver a wide range of public lectures with a focus on pre-college students from historically underrepresented backgrounds who have had limited exposure to theoretical physics and/or quantum sciences. Some of these lectures will be delivered through Northeastern University’s Center for STEM Education. The PI will participate in the Building Bridges Program at Northeastern, an interactive day to introduce prospective college students to the sciences and engineering, and the Young Scholars program at Northeastern, a six-week intensive summer program where rising high-school seniors work on cutting edge research problems and receive mentoring from faculty and university 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.