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

非技术性描述：该项目研究材料在快速应力脉冲下的行为。当一个固体物体在环境温度下受到一个非常快的力的撞击时，人们可以模拟绝对零度下的条件，这是任何物质所能达到的最冷状态。 这是因为，力持续的时间小于原子振动的一个周期，固体中的原子保持静止，以至于它们的行为就像处于最冷的状态一样！为了探索这种可能性，该项目利用该团队最近的一项发明，从超快电子束中产生超快长程力，然后研究在环境温度下材料受到这种力的影响的反应。观察到的结果可能是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。 一个教育计划也被整合到研究中，提供实验室和远程学习，社区推广和新的研究生教科书。技术描述：本项目研究了在亚皮秒，亚原子振动极限下，当原子迁移被冻结，位错和畴壁运动小于一个原子间距时，固体材料的电导率，机械性能和铁电性的应力诱导转变。它为揭示（a）电子-声子相互作用的实时作用，这可能导致电子脱陷，和（B）相干晶体旋转/剪切，这可能导致孪生塑性和纳米畴铁弹性提供了完美的设置。该实验利用了该团队最近的一项发明：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的瞬态电流，从而产生0.1 ps的自作用力。亚ps应力比之前的记录快得多，它挑战了我们在原子水平上对力学行为的基本理解，探测了铁电开关的基本极限，并在真实的时间内表现出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，这些实验可以建立电荷捕获器件的基本速度限制。

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.