EFRI NewLAW: Non-reciprocal, topologically protected propagation using atomically thin materials for nanoscale devices

光学中的相互作用可以用我们熟悉的观察来描述：“如果我能看到你，你也能看到我。“这一现象源于这样一个事实，即在微观层面上控制光及其与物质相互作用的自然法则并不倾向于任何特定的时间方向。换句话说，如果我们假设颠倒时间的方向，自然定律的预测将保持不变。当然，在宏观尺度上，情况并非如此，因为我们从经验中知道，时间之箭有一个固定的方向。事实证明，即使在微观尺度上，外部磁场也可以通过选择优选的传播方向来打破时间的对称性，这可能导致互易性的破坏。在目前的光学设备中，磁铁被用来引起这种光的单向传播，这对于光通信和互联网至关重要。该项目的一个目标是通过使用一类原子级薄的新材料，在不使用磁体的情况下实现光的非互易性。这种材料由于其独特的晶体结构而具有有效的磁场，并且可以代替施加的外部磁场用于光的单向传播。该项目旨在实现基于这些新型材料的小型化光学器件和电路元件，这将允许更快的光开关和减少占地面积的缺陷不敏感传播。这种设备有可能改变光通信行业。在这个项目的过程中，研究团队将提供科学教育和尖端技术的研究经验，以中学，本科和研究生，包括那些学生从历史上的黑人学院和大学，在努力提高科学和工程劳动力的明天。该项目的目标是实现芯片上的，非互易纳米光子器件和电路元件在光频率和拓扑保护的光子边缘状态。这种设备将具有新的功能，如可重新配置的单向传播和光的转向。能量和信息在与时间无关的线性系统中的非互易传播需要打破时间反演对称性，这可以通过外部磁场来实现。我们将实现非互易性传播在纳米尺度上的无磁的方式与外部刺激的主动控制的可能性。我们的方法将采用原子级薄的材料，如过渡金属二硫属化物具有独特的电子和光学性能，以实现这些目标。在这些破坏反转对称的材料中，存在动量空间中的有效磁场，称为贝里曲率。虽然没有净贝里曲率是目前在这些材料中，电控制提供了空间局部时间反演打破和非互易传播的可能性。此外，我们将依靠这些材料中强的光-物质相互作用和非线性来增加非互易性，并实现光的拓扑保护边缘态。为此，将利用增强光-物质相互作用的光学和等离子体纳米腔。该研究项目将推进我们对低维材料中Berry曲率等有效规范场的基本理解，以及如何利用强光物质相互作用来实现光物质的片上可重构非互易性和拓扑状态。

Reciprocity in optics can be described by the familiar observation: "If I can see you, you can see me." This phenomenon stems from the fact that laws of nature governing light and its interaction with matter on a microscopic level do not prefer any particular direction of time. In other words, if we were to hypothetically reverse the direction of time, the predictions of the laws of nature would remain unaltered. Of course, at a macroscopic scale, this is not the case as we know from experience that the arrow of time has a fixed direction. It turns out that an external magnetic field can break the symmetry of time even at the microscopic scale by picking a preferred direction of propagation, which can lead to a break down of reciprocity. In current optical devices, magnets are used to cause such a one-way propagation of light, which is crucial for optical communications and the Internet. One goal of this project is to achieve non-reciprocity of light without the use of magnets by using a new class of materials, which are atomically thin. Such materials feature an effective magnetic field due to their unique crystal structure and can be used in lieu of an applied external magnetic field for one-way propagation of light. This project aims to realize miniaturized optical devices and circuit elements based on these novel materials, which will allow for faster optical switches and defect-insensitive propagation on a reduced footprint. Such devices have the potential to transform the optical telecommunication industry. During the course of this project, the research team will provide science education and research experiences in cutting-edge technologies to middle school, undergraduate and graduate students, including those students from Historically Black Colleges and Universities, in an effort to enhance the science and engineering workforce of tomorrow. The goal of this project is to realize on-chip, non-reciprocal nanophotonic devices and circuit elements operating at optical frequencies and topologically protected edge states for photons. Such devices will feature novel functionalities such as reconfigurable one-way propagation and steering of light. Non-reciprocal propagation of energy and information in a time-independent and linear system requires broken time-reversal symmetry, which can be achieved by an external magnetic field. We will achieve non-reciprocal propagation at nanoscale in a magnetic-free way with the possibility of active control by external stimuli. Our approach will employ atomically thin materials such as transition metal dichalcogenides with unique electronic and optical properties to achieve these goals. In these materials, which break inversion symmetry, an effective magnetic field in the momentum-space called the Berry curvature is present. Although no net Berry curvature is present in these materials, electric control offers the possibility of spatially local time-reversal breaking and non-reciprocal propagation. In addition, we will rely on the strong light-matter interactions and non-linearity in these materials to increase non-reciprocity and also to realize topologically protected edge states of light. To this end, optical and plasmonic nano-cavities, which enhance light-matter interactions, will be exploited. This research project will advance our fundamental understanding of effective gauge-fields like Berry curvature in low-dimensional materials and how strong light-matter interactions can be exploited to achieve on-chip, reconfigurable non-reciprocity and topological states of light-matter.