Sub-Picosecond Stress-Induced Conductivity Transitions, Mechanical Transitions and Ferroelectric Transitions

亚皮秒应力引起的电导率转变、机械转变和铁电转变

• 批准号: 1409114
• 负责人: I-Wei Chen
• 金额: $ 40万
• 依托单位: University of Pennsylvania
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1409114&HistoricalAwards=false
• 关键词: Sub; Picosecond; Stress; Induced; Conductivity

Nontechnical Description: This project investigates material behavior under a fast stress pulse. When a solid object is hit by a very fast force under ambient temperature, one could simulate the condition under absolute zero temperature, which is the coldest state any substance can attain. This is because, with the force lasting less than one period of atomic vibration, atoms in the solid stay so still that they behave as if they were at the coldest state! To probe this possibility, this project utilizes a recent invention of the team to generate an ultrafast long-range force from an ultrafast electron bunch, and then study the response of materials hit by such force, at ambient temperature. The results observed may hold the key to some fundamental materials science questions as well as certain technological ones, such as how fast an electronic device can turn on-and-off. An education plan is also integrated into the research to provide laboratory and distal learning, community outreach and new graduate textbooks.Technical Description: This project investigates stress-induced transitions of conductivity, mechanical properties and ferroelectricity of solid materials at the sub-picosecond, sub-atomic-vibration limit when atomic migration is frozen and dislocation and domain wall movement is less than one atomic spacing. It provides the perfect setting for revealing (a) the real-time action of electron-phonon interaction, which can cause electron de-trapping, and (b) coherent crystal rotation/shear, which can cause twinning plasticity and nanodomain ferroelasticity. The experiments utilize a recent invention of the team: the relativistic magnetic field of a 20 GeV electron/positron bunch can induce, in a metal-insulator-metal structure, a 0.1 ps transient current that generates a 0.1 ps self-force. Much faster than the prior record of ~1 ns stressing, sub-ps stressing challenges our fundamental understanding of mechanical behavior at the atomic level, probes the fundamental limit of ferroic switching, and manifests electron-phonon interactions in condensed matter in real time. As such interactions are often involved in charge trapping and de-trapping, these experiments can establish the fundamental speed limit for charge-trapping devices.

非技术描述：该项目研究快速应力脉冲下的材料行为。当固体物体在环境温度下受到非常快的力撞击时，可以模拟绝对零温度下的情况，这是任何物质可以达到的最冷状态。 这是因为，当力持续不到一个原子振动周期时，固体中的原子会保持静止，以至于它们的行为就像处于最冷状态一样！为了探讨这种可能性，该项目利用该团队最近的一项发明，从超快电子束产生超快远程力，然后研究在环境温度下受到这种力撞击的材料的响应。观察到的结果可能是解决一些基本材料科学问题以及某些技术问题的关键，例如电子设备的开关速度有多快。 研究中还纳入了一项教育计划，以提供实验室和远程学习、社区外展和新的研究生教科书。技术描述：该项目研究了亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒、亚皮秒等应力诱导固体材料的电导率、机械性能和铁电性转变。 -当原子迁移被冻结并且位错和畴壁运动小于一个原子间距时的原子振动极限。它为揭示（a）电子-声子相互作用的实时作用（可能导致电子去俘获）和（b）相干晶体旋转/剪切（可能导致孪晶塑性和纳米域铁弹性）提供了完美的设置。该实验利用了该团队的一项最新发明：20 GeV 电子/正电子束的相对论磁场可以在金属-绝缘体-金属结构中感应出 0.1 ps 瞬态电流，从而产生 0.1 ps 自力。亚皮秒应力比之前约 1 ns 应力的记录快得多，挑战了我们对原子水平机械行为的基本理解，探索了铁电开关的基本极限，并实时显示了凝聚态物质中的电子-声子相互作用。由于这种相互作用通常涉及电荷捕获和去捕获，因此这些实验可以确定电荷捕获器件的基本速度限制。