CAREER: Ultrafast Magnetism in Complex Materials: Coherent and Cooperative Phenomena

*非技术**现在对基础科学和技术提出的一个主要挑战是在十万亿分之一秒内检测、理解和控制复杂系统中的自旋--纳米磁铁的集合。一方面，由相互连接的单个纳米磁性构建块组成的复杂结构可以显示出有价值的特性和改进的功能，这与它们的组件的总和是根本不同的。另一方面，这种动态磁过程至少比迄今使用的传统热磁过程快1000倍，从而极有希望超过现代磁光记录工业中的磁开关速度上限(0.1-10 GHz)，并实现极高速的磁存储/逻辑设备。该提案确定了通过利用中红外和远红外(每秒万亿次)电磁辐射的超短闪光来解决这些问题的一些重大机会。这一“超快自旋挑战”的成功将揭示先进磁系统中尚未被发现的动态过程，并为已确定的问题提供最终的解决方案。该建议包括相互关联的具体教育和推广计划，涵盖高中教师和他们的学生、本科生和研究生水平的学生培训；寻求吸引和留住有才华的学生在科学职业生涯中，并在他们的成功之路上指导他们；开发新课程，与强调超快激光技术的动手实验室模块互补，并与本科生和研究生课程相结合。*技术*该建议使用利用飞秒激光激发的动态磁光光谱方法来探索纳米级和复杂磁系统中的超快磁现象。当今凝聚态物理和材料科学中最具挑战性的问题之一是能否在飞秒时间尺度上探测、理解和控制处于高度非平衡、非热态的宏观磁序。这种工艺比迄今为止使用的传统热磁工艺快至少1000倍，从而极有希望超过现代磁光记录工业中的磁开关速度上限(0.1-10 GHz)，并实现极高速的磁存储/逻辑设备。然而，到目前为止，光激发相干和/或非热载流子如何在这样的时间尺度上实质性地改变宏观有序性的问题到目前为止还没有得到很好的解决，而且大多数预测的光驱动磁系统的奇异性质还没有被观察到。这一提议将探索光致非热飞秒磁相变，并极大地提高我们对远离平衡的量子自旋系统的认识。该提案包括相互关联的具体教育和推广计划，涵盖高中教师和他们的学生、本科生和研究生水平的培训；开发新课程，并与强调超快激光技术的动手实验室模块互补。

*** Non-technical ***One major challenge now being posed for fundamental science and technology is to detect, understand and control spins-an ensemble of nanomagnets-in complex systems within one hundred quadrillionth of a second. On one hand, the complex structures made of inter-connected, individual nano-magnetic building blocks can exhibit valuable characteristics and improved functionalities, which are fundamentally different from the sum of their components. On the other hand, such dynamic magnetic processes are at least 1000 times faster than those of the traditional thermal-magnetic processes used thus far, and thereby carry great promise to exceed the upper limit of the magnetic switching speed (0.1-10 GHz) in modern magneto-optical recording industry and enable extremely high-speed magnetic storage/logic devices. This proposal has identified some major opportunities to address these problems via exploiting ultrashort flashes of mid-infrared and far-infrared (trillion cycles per second) electromagnetic radiation. Success in this "ultrafast spin challenge" will reveal as-yet-undiscovered dynamic processes in advanced magnetic systems, and offer ultimate solution towards the problems indentified. The proposal consists of interconnected, specific plans for education and outreach that span high school teachers and their students, undergraduate and graduate level student training; seeks to attract and keep talented students in careers in sciences, and mentor them along their journey to success; develop new courses with complementary hands-on laboratory modules emphasizing ultrafast laser technology, coupled to undergraduate and graduate curriculum.*** Technical ***This proposal explores ultrafast magnetic phenomena in nanoscale and complex magnetic systems using dynamic magneto-optical spectroscopic methods exploiting femtosecond laser excitations. One of the most challenging questions in condensed matter physics and materials science today is whether one can detect, understand and control macroscopic magnetic orders in their highly non-equilibrium, non-thermal states at femtosecond time scales. Such processes are at least 1000 times faster than those of the traditional thermal-magnetic processes used thus far, and thereby carry great promise to exceed the upper limit of the magnetic switching speed (0.1-10 GHz) in modern magneto-optical recording industry and enable extremely high-speed magnetic storage/logic devices. However, thus far how photoexcited coherence and/or non-thermal carriers can substantially modify the macroscopic ordering at such time scales has been poorly addressed to date and most of the predicted exotic properties of photo-driven magnetic systems have yet to be observed. This proposal will explore photoinduced non-thermal, fs magnetic phase transition and significantly advance our knowledge of quantum spin systems driven far from the equilibrium. The proposal consists of interconnected, specific plans for education and outreach that span high school teachers and their students, undergraduate and graduate level student training; develop new courses with complementary hands-on laboratory modules emphasizing ultrafast laser technology.