Transport and Optical Phenomena in Correlated Electron Systems

非技术总结该奖项是对具有非传统电子行为的材料的输运和光学性质的理论研究。对凝聚态系统中输运和光学现象的研究提供了关于电子动力学以及它们如何相互作用和原子振动的宝贵信息。然而，对大量实验数据的分析和解释从来都不是直截了当的，而且往往具有挑战性，因为有许多相互竞争的过程。即使在描述简单的传统金属(如铜和铝)中的电子传输时，人们也会遇到这样的挑战，在这些金属中，电子的行为几乎是自由粒子。在强电子-电子相互作用消除了与自由电子图像的任何相似之处的材料中，分析变得更加复杂。在这个项目中，Pi和他的团队将研究几个非传统系统的输运和光学性质，例如那些强相互作用导致电阻率与温度成线性关系的系统，电子的能量以线性方式依赖于其动量的系统，以及其中电偶极矩的自发排列被原子的量子运动克服的材料。研究这些令人费解的系统不仅对促进我们对材料的科学理解很重要，而且它们还可能在未来导致技术创新，例如在无损传输电和量子信息科学方面。该奖项还支持教育和推广活动。国际物理学会将为凝聚态物理高级主题多教员课程开发与这一奖项相关的主题的新模块，采用和修改历史/物理联合课程，从科学和历史的角度对物理发现进行双重探索，组织各种讲习班和会议，并针对高年级本科生和研究生编写一本关于物理中的定量方法的新书。技术总结这个项目需要对非常规电子系统的传输和光学特性进行理论研究。这项研究有三个主要目标。在第一个推力中，PI和他的团队将专注于双层石墨烯中的自旋集体模理论，该理论具有邻近诱导的Rashba和山谷-Zeeman类型的自旋-轨道耦合，这将为具有多电子谷、自旋-动量锁定和非阿贝尔Berry曲率的费米-液体理论提供新的发展。第二个目标是发展电子-电子和电子-空穴相互作用诱导的Dirac和Weyl半金属的本征光学吸收的详细理论。在这项工作的第一阶段，Pi的团队将在伴随Hubbard和Coulomb相互作用的低能单粒子哈密顿量水平上研究模型系统中的光吸收。随后，该小组将转向更现实的、依赖于材料的哈密顿量，并对真实材料中的光吸收做出具体预测。第三个目标是从理论上描述在掺杂的量子顺电材料中观察到的几个令人费解的现象，如钛酸锶。在这个目标范围内要讨论的主题包括：(I)电阻率的二次入温行为的起源；(Ii)没有准粒子的热金属中电荷和热传输的适当描述，以及超出普朗克极限的电荷和热传输；(Iii)有效质量的强烈温度依赖性的起源，如光学和热电效应；以及(Iv)准线性和准各向同性磁阻的起源。该奖项还支持教育和推广活动。国际物理学会将为凝聚态物理高级主题多教员课程开发与此奖项相关的主题的新模块，采用和修改历史/物理联合课程，从科学和历史的角度对物理发现进行双重探索，组织各种研讨会和会议，并针对高年级本科生和研究生编写一本关于物理学中定量方法的新书。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NONTECHNICAL SUMMARYThis award theoretical research on transport and optical properties of materials with unconventional electronic behavior. Investigations of transport and optical phenomena in condensed matter systems provides invaluable information about the dynamics of electrons and how they interact with each other and atomic vibrations. However, the analysis and interpretation of abundant experimental data is never straightforward and, quite often, challenging, due to a multitude of competing processes. One encounters such challenges even when describing electron transport in simple conventional metals, such as copper and aluminum, where electrons behave as almost free particles. Analysis becomes even more complicated in materials where strong electron-electron interaction erases any similarities with the free-electron picture. In this project, the PI and his team will investigate transport and optical properties of several unconventional systems, such as those where the strong interaction leads to a linear temperature dependence of the resistivity, systems where the electron's energy depends on its momentum in a linear fashion, and materials in which the spontaneous alignment of electric dipole moments is overcome by the quantum motion of the atoms. Studying these puzzling systems is not only important for advancing our scientific understanding of materials in general, but they could also potentially lead to technological innovations in the future, such as in lossless transmission of electricity and quantum information science.This award also supports educational and outreach activities. The PI will develop new moduli on subjects relevant to this award for a multi-faculty course on Advanced Topics in Condensed Matter Physics, adopt and revamp a joint History/Physics course that offers a dual exploration of physics discoveries from scientific and historical points of view, organize various workshops and conferences, and work on a new book on Quantitative Methods in Physics aimed at upper-undergraduate and graduate students. TECHNICAL SUMMARYThis project entails theoretical research on transport and optical properties of unconventional electronic systems. The research has three main objectives. In the first thrust, the PI and his team will focus on the theory of spin collective modes in bilayer graphene with proximity-induced Rashba and valley-Zeeman types of spin-orbit coupling, which will provide a new development in the Fermi-liquid theory with multiple electron valleys, spin-momentum locking, and non-Abelian Berry curvature. The second objective is to develop a detailed theory of intrinsic optical absorption in Dirac and Weyl semi-metals, induced by electron-electron and electron-hole interactions. At the first stage of this effort, the PI’s group will study optical absorption in model systems, at the level of low-energy single-particle Hamiltonians, accompanied by both Hubbard and Coulomb interaction. Subsequently, the group will turn to more realistic, material-dependent Hamiltonians and make specific predictions for optical absorption in real materials. The third objective is to describe theoretically several puzzling phenomena observed in doped quantum paraelectrics such as strontium titanate. The topics to be addressed within this objective include (i) the origin of the quadratic-in-temperature behavior of the resistivity; (ii) a proper description of charge and heat transport in a thermal metal without quasiparticles, and beyond the Planckian limit, (iii) the origin of a strong temperature dependence of the effective mass, as measured by optics and thermoelectric effect; and (iv) the origin of quasi-linear and quasi-isotropic magnetoresistance.This award also supports educational and outreach activities. The PI will develop new moduli on subjects relevant to this award for a multi-faculty course on Advanced Topics in Condensed Matter Physics, adopt and revamp a joint History/Physics course that offers a dual exploration of physics discoveries from scientific and historical points of view, organize various workshops and conferences, and work on a new book on Quantitative Methods in Physics aimed at upper-undergraduate and graduate students.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.