EFRI NewLAW: Magnetic Field Free Magneto-optics and Chiral Plasmonics with Dirac Materials

大多数自然现象都遵循“时间反转对称性”，即如果时间方向反转，例如，光波在向前和向后的传播方向是相同的。但是，光传输只允许光单向通过，被称为非互易传播，对于电信中的能量减少和噪声抑制至关重要。非互易性的产生需要打破时间反转对称性，通常可以通过法拉第效应(穿过材料的光受到外部磁场的影响，从而改变光波方向)在磁光材料中实现。这种对外部磁场的基本要求大大限制了器件的小型化和片上集成。该计划研究一种新的材料平台“带隙狄拉克材料”，其固有的Berry曲率，即其能带结构的关键和新认识的属性，可以作为有效磁场-从而产生独特的手征边缘等离子体共振，可以促进非互易光的传播。这项研究的成果将使用于光通信和量子信息处理的紧凑、无磁场(从而轻便且节能)的可调谐非互易器件成为可能。该项目将在多学科环境中培训STEM的研究生和未被充分代表的学生；通过教师研究经验、“科学上的自来水”公开讲座和以中学女生为重点的“拓宽视野”等项目向公众提供宣传；并在开放源码许可下开发和分发分析工具和代码。该项目探索基于过渡金属二卤化物单层等狄拉克材料的磁光和无磁场非互易光传输的新前沿，其中反转对称性的破坏和大的自旋-轨道耦合导致山谷-自旋锁定。这些材料的本征Berry曲率进一步充当了动量空间中的有效磁场，在山谷不平衡的情况下，可以产生手征等离子体模，使得光在中红外和太赫兹频率下能够非互易地传播。这些带隙Dirac材料中的谷极化将通过三种方法来诱导：1)过渡金属杂质掺杂；2)接近层状磁性过渡金属磷三盐化合物；3)电子自旋注入。电磁模拟和计算选定的单分子膜和异质结中的Berry曲率、磁光效应和手性等离子体，将为分子束外延和化学气相沉积材料的合成、原子尺度的自旋分辨扫描隧道显微镜/光谱、角度分辨光电子能谱和偏振选择光致发光表征以及远场光学表征和近场扫描光学显微镜成像提供指导。通过实验和理论相结合的方法，该项目旨在展示中红外到太赫兹范围内的波导手性等离子体，以实现非互易法拉第光隔离器和可调光环行器等无磁场光学器件。

Most natural phenomena obey "time-reversal symmetry", which states that if the direction of time is reversed, for example, the propagation of light waves is the same in both forward and backward directions. But optical transport that only lets light pass one-way, termed "non-reciprocal propagation", is vital for energy reduction and noise suppression in telecommunications. The generation of non-reciprocity requires breaking time-reversal symmetry, and typically can be realized in magneto-optical materials via the Faraday effect (where light passing through a material is subject to an external magnetic field, thus changing the light wave orientation). This fundamental requirement of an external magnetic field places significant limitations on device miniaturization and on-chip integration. This program researches a new material platform "gapped Dirac materials" whose intrinsic Berry curvature, a key and newly-recognized property of their energy band structure, can act as an effective magnetic field - thus giving rise to unique chiral edge plasmon resonances that can facilitate non-reciprocal light propagation. The outcome of this research will enable compact, magnetic-field-free (and thus lightweight and energy-efficient) tunable nonreciprocal devices for optical communications and quantum information processing. This project will train graduate and under-represented students in STEM in a multidisciplinary environment; provide outreach to the public through programs such as Research Experience for Teachers, "Science on Tap" public lectures, and "Broaden the Horizon" that focuses on middle school female students; and develop and distribute analysis tools and codes under open source licenses.This project explores a new frontier in magneto-optics and magnetic-field-free non-reciprocal light transport based on Dirac materials such as transition-metal dichalcogenide monolayers, where the breaking of inversion symmetry and large spin-orbit coupling lead to valley-spin locking. The intrinsic Berry curvature of these materials further acts as an effective magnetic field in momentum space, which under a valley imbalance can give rise to chiral plasmon modes that enable non-reciprocal light propagation at mid infrared and terahertz frequencies. Valley polarization in these gapped Dirac materials will be induced through three approaches: 1) doping with transition-metal impurities; 2) proximity to layered magnetic transition-metal phosphorous trichalcogenides; and 3) electrical spin injection. Electromagnetic modeling and calculations of the Berry curvature, magneto optical effects, and chiral plasmons in selected monolayers and heterostructures will provide guidance for material synthesis by molecular beam epitaxy and chemical vapor deposition, and atomic scale characterization with spin-resolved scanning tunneling microscopy/spectroscopy, angle-resolved photoemission spectroscopy, and polarization selective photoluminescence, as well as far-field optical characterization and near-field scanning optical microscopy imaging. Through an integrated experimental-theoretical approach, this project aims to demonstrate wave guiding chiral plasmons in the mid-infrared to terahertz range to enable magnetic-field-free optical devices such as non-reciprocal Faraday isolators and tunable optical circulators.