Topological Physics and Light Matter Interactions: From Floquet Topological Insulators to Solar Cells

非技术总结材料研究部和物理部为该奖项提供资金，该奖项支持理论研究和教育，重点是通过各种系统中的光-物质相互作用来稳定和利用拓扑行为的方法。拓扑绝缘体具有一些令人惊讶的特性，例如在其内部绝缘的同时，在其边界处导电而不耗散的能力。将在该奖项下进行的研究旨在扩展物质与光相互作用时的拓扑行为的概念。这为基础研究和应用研究提供了肥沃的土壤。这项研究将围绕三个主题展开。第一种是使用拓扑绝缘体表面来收集能量和探测红外线。二是利用光将普通绝缘体变成拓扑型绝缘体。第三个是在腔内半导体的混合系统中创建独特的边缘状态，该系统可以连接半导体和光学技术。这项研究有可能引入新的能量收集和光探测技术，并为基于拓扑原理的新型光子器件铺平道路。该奖项将允许在材料物理和光学交叉的跨学科研究环境中培训研究生和博士后。PI将让本科生参与这项研究，并将研究材料纳入他在加州理工大学开发的本科水平课程。技术总结材料研究部和物理部为该奖项提供资金，该奖项支持理论研究和教育，重点是通过各种系统中的光-物质相互作用稳定和利用拓扑行为的方法。该项目的第一部分专注于将三维(3D)拓扑绝缘子的表面转变为针对难以捉摸的中波长红外光谱的光伏平台。尽管存在许多电子-空穴对形成的事实，但3D拓扑绝缘体的表面电子通常对入射光具有微小的光电流响应。PI将利用表面上的自旋轨道锁定将其转变为光电流整流器。这可以使用沉积在表面上的磁栅来完成，这应该会导致对圆偏振光的实质性光电流响应。PI将考虑这种效应在现实的拓扑绝缘体中的表现，它相对于沉积的磁图形的优化，以及它对其他系统的扩展，例如二维(2D)拓扑绝缘体和具有Rashba相互作用的2D量子阱。在第二部分中，PI将研究使用相干光在平凡的半导体中诱导拓扑行为的方法。被驱动进入拓扑相的半导体中的电子呈现出由驱动强度和各种弛豫机制决定的非平衡能量分布。通过推导这些分布，PI将研究在什么情况下非平衡效应不会阻碍被驱动系统的拓扑行为，并分析检测这种所谓的Floquet拓扑相的方案。该项目的第三部分集中在在耦合到平凡半导体的光波导中产生拓扑极化子态的可能性。依赖于Floquet拓扑绝缘体的思想，PI将研究在拓扑平凡的半导体量子阱中是否可能存在腔光子和激子的拓扑束缚态。拓扑极化子态可以表现出很强的寿命增强，也可以用作纳米光子隔离器。这项研究有可能引入新的能量收集和光探测技术，并为基于拓扑原理的新型光子器件铺平道路。该奖项将允许在材料物理和光学交叉的跨学科研究环境中培训研究生和博士后。PI将让本科生参与这项研究，并将研究材料纳入他在加州理工大学开发的本科课程。

NON-TECHNICAL SUMMARYThe Division of Materials Research and the Division of Physics contribute funds to this award which supports theoretical research and education focused on means to stabilize and utilize topological behavior through light-matter interactions in a variety of systems. Topological insulators possess some amazing properties such as the ability to conduct electricity without dissipation at their boundaries while being insulating through their interior. The research which will be carried out under this award is geared toward extending concepts of topological behavior of matter when it interacts with light. This presents a fertile ground for fundamental and applied research. The research will concentrate on three themes. The first is to employ topological insulator surfaces for energy harvesting and detection of infra-red light. The second is to use light to turn an ordinary insulator into a topological insulator. The third is to create unique edge states in a hybrid system of a semiconductor in a cavity that could bridge semiconductor and optical technologies. This research has the potential of introducing new techniques for energy harvesting and light detection and paving the way to new photonic devices based on topological principles. The award will allow training of graduate students and postdocs in an interdisciplinary research environment at the intersection of materials physics and optics. The PI will involve undergraduate students in this research and incorporate the research material into the undergraduate level course that he has developed at Caltech.TECHNICAL SUMMARYThe Division of Materials Research and the Division of Physics contribute funds to this award which supports theoretical research and education focused on means to stabilize and utilize topological behavior through light-matter interactions in a variety of systems. The first part of the project is focused on turning the surface of three-dimensional (3D) topological insulators into a photovoltaic platform aimed at the elusive mid-wavelength infrared spectrum. The surface electrons of 3D topological insulators typically have a minute photocurrent response to incident light in spite of the fact that many electron-hole pairs form. The PI will exploit the spin-orbit locking on the surface to turn it into a photocurrent rectifier. This can be done using a magnetic grating deposited on the surface which should result in a substantial photocurrent response to circularly polarized light. The PI will consider the manifestations of this effect in realistic topological insulators, its optimization with respect to the magnetic pattern deposited, and its extension to other systems, such as two-dimensional (2D) topological insulators and 2D quantum wells with Rashba interaction. In the second part the PI will study ways to induce topological behavior in trivial semiconductors using coherent light. Electrons in semiconductors driven into a topological phase exhibit a non-equilibrium energy distribution determined by the strength of the drive and various relaxation mechanisms. By deriving these distributions, the PI will investigate under what circumstances the non-equilibrium effects do not obstruct the topological behavior of the driven system, and analyze schemes to detect this so-called Floquet topological phase.The third part of the project is focused on the possibility of creating topological polariton states in optical waveguides coupled to trivial semiconductors. Relying on the idea of the Floquet topological insulator, the PI will examine whether it is possible to have a topological bound state of a cavity photon and an exciton in a topologically trivial semiconducting quantum well. A topological polariton state may exhibit strongly enhanced lifetimes, as well as could be used as a nanophotonic isolator. This research has the potential of introducing new techniques for energy harvesting and light detection and paving the way to new photonic devices based on topological principles. The award will allow training of graduate students and postdocs in an interdisciplinary research environment at the intersection of materials physics and optics. The PI will involve undergraduate students in this research and incorporate the research material into the undergraduate level course that he has developed at Caltech.