Symmetry, entanglement, and far-from equilibrium perturbations in 2D materials

摘要：晶体晶格是晶体内部原子的几何排列。理论方法通常依赖于材料具有完美周期晶格的假设。然而，在现实中，无序——以缺陷、空缺或其他一些协同原子调制的形式——是相当常见的，与潜在的相互作用相关，可以成为新的和有趣的行为的驱动因素。该项目的目标是推进关于晶格在可变长度和时间尺度上的作用和性质的基本知识，从而预测其物理性质。具体来说，一类被称为过渡金属二硫族化合物（TMDs）的准二维化合物将被研究，因为它们提供了令人难以置信的丰富的新颖和鲜为人知的性质。由简单的堆叠原理构成，过渡金属层与硫离子层交替。tmd在广泛的科学环境中非常重要，并且由于其可调特性，可以在许多技术中找到自己的方法。该项目旨在确定tmd的通用特征和控制其属性的方法。本研究将采用新颖的泵浦探针实验技术和中子散射，为学生提供尖端实验技术的训练机会，并让他们接触到新的能力。技术摘要：理论方法通常依赖于材料具有完美周期性晶格的假设，但在现实中，以缺陷，空位或其他一些协同原子调制形式出现的无序是非常常见的，与潜在的相互作用相关，并且可以成为新的和有趣的行为的驱动因素。该项目的主要目标是确定相关长度和时间尺度上的晶格扭曲，以及它们对真实材料中自旋和电子自组织方式的影响——定义特征电荷密度波（CDW）调制的新局部模式，以及可能作为1T-MX2 （M = Ta, X = S， Se或Te）中量子自旋液体（QSLs）证据的新磁特征。该项目提供了一个机会来探索一种奇特的超导形式，因为它与QSL非常接近，并试图获得cdw向超导和QSL状态转变的基本理解。将通过等价掺杂研究无序和降维对热平衡和非平衡状态下的静态和动态性能的影响。该研究结合了高分辨率和高强度中子和x射线散射技术，以及使用单晶和粉末的实空间分析探针，并辅以热力学测量。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。

Non-technical Abstract: A crystal lattice is the geometrical arrangement of atoms inside a crystal. Theoretical approaches often rely on the assumption that materials have perfectly periodic lattices. However, in reality, disorder - in the form of defects, vacancies, or some other cooperative atomistic modulation - is quite common and relevant to the underlying interactions and can be the driver for new and interesting behaviors. The goal of this project is to advance fundamental knowledge on the role and properties of the crystal lattice across variable length and time scales, allowing for predictions of physical properties. Specifically, a family of quasi-two dimensional compounds known as transition metal dichalcogenides (TMDs) will be investigated as they offer an incredibly rich range of novel and poorly understood properties. Constructed by simple stacking principles, layers of a transition metal alternate with a chalcogen ion. TMDs are important in a broad scientific context, and can find their way to many technologies because of their tunable characteristics. This project seeks to identify universal features of TMDs and ways to control their properties. Novel pump-probe experimental techniques and neutron scattering will be used in the course of this study, providing students with training opportunities in cutting-edge experimental techniques and exposing them to novel capabilities. Technical Abstract: Theoretical approaches often rely on the assumption that materials have perfectly periodic lattices but, in reality, disorder - in the form of defects, vacancies, or some other cooperative atomistic modulation - is quite common and relevant to the underlying interactions and can be the driver for new and interesting behaviors. The primary objective of this project is to identify lattice distortions at relevant length and time scales, and their effects on how spins and electrons self-organize in real materials - new local patterns that define the characteristic charge density wave (CDW) modulations as well as new magnetic signatures that might serve as evidence of quantum spin liquids (QSLs) in 1T-MX2 (M = Ta, and X = S, Se, or Te). This project provides the opportunity to explore an exotic form of superconductivity given its close proximity to QSL and seeks to obtain a fundamental understanding of CDW-enabled transitions to superconducting and QSL states. The effects of disorder and reduced dimensionality on the static and dynamic properties, at thermal equilibrium and away from equilibrium will be studied through isovalent doping. The research combines high-resolution and high-intensity neutron and x-ray scattering techniques, as well as real-space analysis probes, using single crystals and powders, supplemented by thermodynamic measurements.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.