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，这对开发节能的未来技术有重大影响。我们感兴趣的材料是由两种复合氧化物交替层组成的薄膜，这两种氧化物表现出不同的电极化特性，但结构相似。所得到的薄膜具有高度周期性的极化畴图案，典型尺寸在10纳米范围内。通过将激光脉冲照射在材料上，研究人员动态地修改这些图案的空间顺序。通过频闪测量来研究这些模式的时间演化，其时间分辨率足够快，可以观察到电子运动，从而了解模式形成的潜在机制。寻找光学控制偏振模式的路线可能具有深远的应用。这些图案可以编码信息，这些信息可以被光迅速改变。与传统电子产品相比，这减少了能量消耗，同时使非易失性存储器或计算设备的切换速度提高了许多数量级。该项目包括教育活动，旨在培养物理、化学和材料科学领域的下一代科学家和工程师。这些活动将吸引K-12学生、本科生和研究生以及其他社区成员，以促进STEM领域的多样性，并提供宝贵的培训机会。技术描述：本项目研究拓扑超晶格中的非平衡态和光致跃迁。研究了由钛酸锶和钛酸铅交替层组成的铁电/准电异质结构（STO-PTO）。这些异质结构表现出各种局部电极化的拓扑排列，形成了接近平衡的长程极涡和天幕。虽然传统的调谐旋钮，如成分、应变和温度只影响近平衡特性，但超快激光技术的快速改进为动态操纵这些空间复杂的偏振特性提供了新的机会。采用特定于部分本质复杂的STO-PTO系统的超快泵浦-探针方案来研究非平衡相和局部拓扑的时间演化。利用超快宽带极紫外吸收光谱（UBXAS）和极紫外二次谐波产生（XUV-SHG）等新型实验工具，测量了超晶格有序参数，跟踪了光激发后的能量弛豫过程，并实时检测了界面上的近似破对称状态。应用超快电子显微镜（UEM）揭示了极性粒子序的实空间动力学和拓扑缺陷对长程序的影响。该项目为中尺度系统中界面和缺陷介导的相关性提供了新的见解。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。

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