Controlling Quantum Materials: Exotic Orders and Light-Induced Dynamics

什么原理支配着结晶固体中电子的集体量子行为？可以通过控制维度来调整电子的量子相位吗？光可以用来控制和切换电子的多体量子态吗？探索这些重要问题对于获得对量子凝聚态系统的基本理解至关重要，它是创造和控制量子材料的关键，可以为下一代量子技术奠定基础。晶体中电子的平衡和动力学性质是由量子力学定律以及编码在泡利不相容原理中的量子统计所控制的。这种晶体的例子，包括半导体工业的主力硅，在能带理论和费米液体理论的框架内得到了很好的理解。然而，当强电子相互作用在晶体中变得重要时，电子可以组织成显着的新状态，从而导致超导性，巨磁电阻或电子液晶。过渡金属氧化物提供了这种“涌现”行为的典型例子，展示了大量新的集体相，具有固态驱动器，催化剂和光伏等一系列应用。近年来，人们已经认识到相对论性自旋轨道耦合可以赋予固体中的电子带新的拓扑特征，具有新型器件的潜力和量子计算领域的新方向。该提案中概述的五年研究计划侧重于两个相互交织的研究线索。第一个线程旨在探索和理解出现在量子材料中的奇异序的光学性质，如重过渡金属氧化物、卤化物和硫族化物。这些量子材料表现出强烈的原子自旋轨道耦合，从而导致拓扑相，非常规超导和磁序的出现，无论是在块状晶体中，还是在二维薄膜和界面中。研究的第二条相互交织的线索涉及如何利用光来控制和操纵这些量子材料及其电子相位。提出的研究将集中在光学性质，如太赫兹电导率和克尔效应，超快泵浦-探针动力学，以及利用声子模式的光驱动在物质的电子状态之间切换。提出的研究将利用数值工具，包括Gutzwiller投影波函数技术，高频展开，强耦合展开，以及处理相关电子动力学的新方法。

What principles governs the collective quantum behaviour of electrons in a crystalline solid? Can one tune quantum phases of electrons by controlling dimensionality? Can light be used to control and switch between many-body quantum states of electrons? Exploring these important issues is crucial to gain a fundamental understanding of quantum condensed matter systems, and it holds the key to creating and controlling quantum materials which can lay the foundation for the next generation of quantum technologies. The equilibrium and dynamical properties of electrons in crystals are governed by the laws of quantum mechanics, together with quantum statistics as encoded in the Pauli exclusion principle. Examples of such crystals, which include silicon, the workhorse of the semiconductor industry, are extremely well-understood within the framework of band theory and Fermi liquid theory. However, when strong electron interactions become important in a crystal, the electrons can organize into remarkable new states leading to superconductivity, colossal magnetoresistance, or electronic liquid crystals. Transition metal oxides provide a canonical example of such ``emergent'' behavior, exhibiting a plethora of new collective phases, with a slew of applications such as solid state drives, catalysts, and photovoltaics. In recent years, it has been recognized that relativistic spin-orbit coupling can impart new topological character to electronic bands in solids with the potential for novel devices and the promise of new directions in the field of quantum computing. The five-year research programme outlined in this proposal focuses on two intertwined threads of research. The first thread aims to explore and understand the optical properties of exotic orders which appear in quantum materials such as heavy transition metal oxides, halides, and chalcogenides. These are quantum materials which exhibit strong atomic spin-orbit coupling, which leads to the emergence of topological phases, unconventional superconducting and magnetic orders, both in bulk crystals as well in two-dimensional thin films and interfaces. The second intertwined thread of the research deals with how one might control and manipulate such quantum materials and their electronic phases using light. The proposed research will focus on optical properties such as THz conductivity and Kerr effects, ultrafast pump-probe dynamics, and switching between electronic states of matter using optically driving of phonon modes. The proposed research will utilize numerical tools including Gutzwiller projected wavefunction techniques, high frequency expansions, strong coupling expansions, and novel methods to treat the dynamics of correlated electrons.