Investigation of Nonequilibrium States and Photoinduced Transitions in Topological Superlattices

拓扑超晶格中非平衡态和光致跃迁的研究

• 批准号: 2247363
• 负责人: Michael Zuerch
• 金额: $ 64.72万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2026-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247363&HistoricalAwards=false
• 关键词: Investigation; Nonequilibrium; States; Photoinduced; Transitions

Nontechnical description: This project investigates new ways of manipulating quantum materials with ultrashort laser pulses, which can have a significant impact on developing energy-efficient future technologies. The material of interest is a thin film made up of alternating layers of two types of complex oxides that exhibit different electric polarization properties but are structurally similar. The resulting thin film has a highly periodic pattern of polarization domains with typical sizes in the range of 10 nanometers. By shining laser pulses on the material, the investigators dynamically modify the spatial order of these patterns. Studying the temporal evolution of these patterns by stroboscopic measurements with a temporal resolution fast enough to observe electron movements provides an understanding of the underlying mechanisms of pattern formation. Finding routes to optically control polarization patterns could have far-reaching applications. These patterns can encode information that can be rapidly changed by light. This reduces the amount of energy used compared to conventional electronics while enabling many orders of magnitude faster switching in non-volatile memories or computation devices. This project includes educational activities aimed at training the next generation of scientists and engineers at the interface between physics, chemistry, and materials science. These activities will engage with K-12 students, undergraduate and graduate students, and other members of the community to promote diversity in STEM fields and provide valuable training opportunities.Technical description: This project investigates nonequilibrium states and photoinduced transitions in topological superlattices. The research focuses on a ferroelectric/paraelectric heterostructure composed of alternating strontium titanate and lead titanate layers (STO-PTO). These heterostructures exhibit a variety of topological arrangement of local electric polarization forming long-range orders of polar vortices and skyrmions near equilibrium. While traditional tuning knobs like composition, strain, and temperature only affect near-equilibrium properties, rapid improvements in ultrafast laser technology presents a new opportunity to dynamically manipulate these spatially-complex polarization properties. Ultrafast pump-probe schemes specific to parts of the intrinsically complex STO-PTO system is used to investigate the temporal evolution of out-of-equilibrium phases and local topology. Novel experimental tools, including ultrafast broadband extreme-ultraviolet absorption spectroscopy (UBXAS) and extreme ultraviolet second harmonic generation (XUV-SHG), are used to measure superlattice order parameters, trace energetic relaxation processes following photoexcitation, and detect proximitized broken-symmetry states at the interface in real-time. Ultrafast electron microscopy (UEM) is applied to unravel real-space dynamics of the polar skyrmion order and the impact of topological defects on long-range order. The project provides novel insights into interface and defect-mediated correlations in mesoscale systems.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.

非技术描述：该项目研究了用超短激光脉冲操纵量子材料的新方法，这可能会对开发节能的未来技术产生重大影响。感兴趣的材料是由两种类型的复杂氧化物的交替层组成的薄膜，它们具有不同的电化特性，但在结构上是相似的。所得的薄膜具有高度周期性的极化域模式，其典型尺寸在10纳米范围内。通过在材料上发光激光脉冲，研究人员会动态修改这些模式的空间顺序。通过瞬时分辨率快速研究这些模式的时间演变，可以快速观察电子运动，从而了解了对模式形成的基本机制的理解。寻找光学控制极化模式的途径可能具有深远的应用程序。这些模式可以编码可以通过光快速更改的信息。与常规电子设备相比，这减少了所使用的能量量，同时可以在非挥发性记忆或计算设备中更快地切换许多数量级。该项目包括旨在培训下一代科学家和工程师在物理，化学和材料科学之间的接口的教育活动。这些活动将与K-12学生，本科生和研究生以及社区的其他成员互动，以促进STEM领域的多样性并提供宝贵的培训机会。技术描述：该项目调查了非平衡状态和拓扑超级晶格中的光诱导的过渡。该研究的重点是由钛酸标和钛酸铅（STO-PTO）组成的铁电/副型异质结构。这些异质结构表现出各种局部电化极化的拓扑布置，形成了平衡附近的极性涡流和天空的长期顺序。虽然传统的调整旋钮（如组成，应变和温度）仅影响近平衡性能，但超快激光技术的快速改进为动态操纵这些空间复杂的极化特性提供了新的机会。特定于本质上复杂的STO-PTO系统部分的超快泵探针方案用于研究平衡阶段和局部拓扑的时间演变。新型实验工具，包括超快宽带极端硫化物吸收光谱（UBXA）和极端紫外线第二次谐波生成（XUV-SHG），用于测量超晶格订单参数，痕量能量能量的弛豫过程，在实时的接口处进行了光泽并检测到粘合的破碎状态之后，在实时的接口处进行了分配的断裂状态。超快电子显微镜（UEM）应用于极性天空顺序的真实空间动力学，以及拓扑缺陷对远程顺序的影响。该项目提供了对中尺度系统中界面和缺陷介导的相关性的新见解。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响评估标准通过评估来支持的。

项目成果

Ultrafast formation of topological defects in a two-dimensional charge density wave

• DOI: 10.1038/s41567-023-02279-x
• 发表时间: 2022-11
• 期刊: Nature Physics
• 影响因子: 19.6
• 作者: Yun Cheng;A. Zong;Lijun Wu;Q. Meng;Weicong Xia;Fengfeng Qi;P. Zhu;Xiaoqun Zou;Tao Jiang;Yanfeng Guo;Jasper van Wezel;A. Kogar;M. Zuerch;Jie Zhang;Yimei Zhu;D. Xiang

Detecting driving potentials at the buried SiO2 nanolayers in solar cells by chemical-selective nonlinear x-ray spectroscopy

• DOI: 10.1063/5.0156171
• 发表时间: 2023-07
• 期刊: Applied Physics Letters
• 影响因子: 4
• 作者: M. Horio;T. Sumi;J. Bullock;Y. Hirata;Masashige Miyamoto;Bailey R. Nebgen;T. Wada;T. Senoo;Y. Tsujikawa;Y. Kubota;S. Owada;K. Tono;M. Yabashi;T. Iimori;Y. Miyauchi;M. Zuerch;I. Matsuda;C. Schwartz;W. Drisdell