Ultrafast Electron Scattering to Understand and Control Material Properties

通过超快电子散射了解和控制材料特性

• 批准号: RGPIN-2019-06001
• 负责人: Siwick, Bradley
• 金额: $ 3.64万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=762587
• 关键词: Ultrafast; Electron; Scattering; Understand; Control

There is currently an enormous, world-wide effort directed at the development and application of new experimental methods that make it possible to directly `watch' the time-evolving structure of matter. These approaches combine state-of-the-art femtosecond lasers (Nobel Prize in Physics, 2018) and sources of either ultrashort Xray or electron pulses to acquire time-resolved diffraction/scattering patterns and images. At the highest time-resolution achievable in these instruments (<100 fs), atomic motion is essentially frozen during an observation and one can completely follow the microscopic dynamics to produce a "molecular movie" of many fundamental processes. The Siwick group has long been a pioneer in the development of lab-scale ultrafast electron scattering methods and their application to a wide range of fundamental problems in materials physics. A very significant breakthrough was made in 2016-2017 with the perfection of RF electron pulse compression methods which pushed time resolution below 100 fs for the first time and resulted in the instrumentation designed, built and operating at McGill being the most powerful of its kind anywhere in the World. This has set the stage for the proposed program of study, focused squarely on the central question of condensed matter physics; understanding the complex interplay between charge, spin, orbital and lattice-structural degrees of freedom that gives rise to the emergent macroscopic properties of materials. Addressing this broad challenge requires further enhancements in instrumentation, including electron spectroscopy (ultrafast q-EELS), improved time, space and momentum resolution and electron beam coherence that will be pursued through the current proposal. Each of these have been enabled by the robust synchronization of RF cavities to femtosecond lasers that we recently developed. Leveraging these tools, we will pursue a series of pressing problems in materials physics: I) To improve our understanding of the fundamental basis of heat and electronic transport in thermoelectric materials using ultrafast electron diffuse scattering and computational materials approaches in order to facilitate new thermoelectric materials discovery. II) To investigate how optical excitation can be used to control the properties of strongly correlated materials. III) To further our understanding of the momentum-dependent couplings within and between lattice and charge degrees of freedom in strongly anisotropic (1D and 2D) materials that determine phenomena as diverse as superconductivity, charge density waves, thermoelectricity, photovoltaicity and carrier mobility in semiconductors and metals. IV) To shed new light on the many processes that follow the absorption of light in photovoltaic materials. This proposed research program directly targets 3 of the 5 the Grand Challenges for the Basic Energy Sciences outlined in a seminal DOE report and is expected to have enormous impact.

目前，有一种巨大的，全球范围的努力，致力于开发和应用新的实验方法，使得可以直接“观察”物质的时间不断发展的结构。这些方法结合了最先进的飞秒激光器（诺贝尔物理学奖，2018年）和Ultrashort X射线或电子脉冲的来源，以获取时间分辨的衍射/散射模式和图像。在这些仪器中可以实现的最高时间分辨率（<100 fs），原子运动基本上是在观察过程中冻结的，并且可以完全遵循微观动力学，以产生许多基本过程的“分子电影”。长期以来，Siwick组一直是实验室规模超快电子散射方法的开发的先驱，并将其应用于材料物理学中的广泛基本问题。 RF电子脉冲压缩方法的完美在2016 - 2017年取得了极大的突破，该方法首次将时间分辨率提高到100 fs以下，并导致仪器在麦吉尔（McGill）设计，建造和运行是世界上最强大的仪器。这为拟议的研究计划奠定了基础，直接集中在凝结物理学的核心问题上。了解电荷，自旋，轨道和晶格结构的自由度之间的复杂相互作用，从而产生了材料的新兴宏观特性。应对这一广泛的挑战需要进一步的仪器，包括电子光谱（超快Q-EELS），改善时间，空间和动量分辨率和电子束相干性，这将通过当前的提案来追求。通过将RF腔与我们最近开发的飞秒激光器的强大同步启用了这些。利用这些工具，我们将采用一系列材料物理学的紧迫问题：i）提高我们对热电材料中热和电子传输的基本基础的理解，并使用超快电子弥漫性散射和计算材料方法来促进新的热电材料发现。 ii）研究如何使用光激励来控制密切相关的材料的性质。 iii）进一步了解我们对强烈各向异性（1D和2D）材料的晶格和电荷自由度之间的动量依赖性耦合，这些材料确定现象与超导性，电荷密度波，热电学，热电压素，光伏和携带者在半径和半多数和METALS和METALS和METALS中的携带者一样多样化。 iv）为遵循光伏材料中光吸收的许多过程提供了新的启示。该拟议的研究计划直接针对5个中的3个，这是针对开创性报告中概述的基本能源科学的巨大挑战，并有望产生巨大影响。