二维原子晶体的表面等离激元诱导光学自旋流和谷电荷流相干注入

Optical radiation on two-dimensional crystals could induce optical charge, spin and valley current injection. The researches of these types of photon-electron interaction provide theoretical foundation for the development of optoelectronic logical devices based on spin and valley current. Surface plasmons could localize optical field, and enhance photon-electron interaction, therefore could enhance nonlinear optical and optoelectronic effect. We found that the interaction between the evanescent wave of the surface plasmon and graphene could enhance the photon drag effect. This project researches the charge, spin and valley current injection of two-dimensional crystals induced by the interaction with surface plasmons. The surface plasmons of mono-atomic layer conducting surfaces have localized inhomogeneous optical field; patterning the surfaces with photonic crystal structures could designs slow light optical modes. Both of these two types of optical modes could enhance photon-electron interaction. In order to explore the mechanism of enhancement and control of spin and valley current injection by interaction with non-classical optical field, this project researches the dynamic properties of electrons in the band structure of the two-dimensional crystals and their Berry phase physics under the excitation of surface plasmons, as well as the coherent evolution of the coupled systems between the electrons and the optical field. The theoretical models being built in the project could help us to further understand the effect of optoelectronic interaction and geometry phase on the dynamic properties of electrons in the band structure of the two-dimensional crystals; it could lay a theoretical foundation for the development of the new generation optoelectronic logical devices.

二维原子晶体受激光照射会产生光致电流、自旋流或谷电荷流。研究这种光电相互作用为基于自旋或谷电荷的光电逻辑器件的发展提供理论依据。表面等离激元使光场局域化、增强光电相互作用，能够增强非线性光学和光电子效应。我们发现表面等离激元的消逝场作用于石墨烯可以增强光拖拽效应。本项目将深入研究表面等离激元作用于二维原子晶体所产生的电流、自旋流和谷电荷流注入。单原子导电层的表面等离激元具有局域非均匀光场；加入光子晶格结构之后能设计慢光子模式。这两种光学模式都能够增强光电相互作用。为了探索非经典光场对自旋流和谷电荷流注入的增强或调控机制，本项目研究在表面等离激元的激发下二维原子晶体的能带电子的运动规律及其贝里相位物理，以及电子与光场的相干演化。本项目所建立的理论模型有助于进一步理解二维材料能带电子的运动受光电作用和几何相位的影响；也对新一代光电逻辑器件的开发奠定理论基础。

随着硅基集成电路的发展，电路线宽已经小于7纳米，将会接近摩尔定律的极限。进一步发展需要利用二维材料等新型纳米体系。构造尺寸小于1纳米的集成电路结构，即进入后摩尔时代。该项目研究二维量子材料的自旋光电子学，有望为新型纳米器件的研发提供原理性理论模型和原型器件。研究内容包括石墨烯和其他二维材料组合而成的多层范德华结构的电子能带，输运，光电子耦合态，以及对边缘态和拓扑界面态的调控。一部分研究针对多层二维材料自身的自旋电子学特性。研究发现双层石墨烯在各种衬底环境下，其拓扑相和边缘态可以受到调控。其中反铁磁范德华自旋阀表现出最好的性能，电子关联可以增强自旋阀的开关比。单层二硫化钼和反铁磁无机钙钛矿组成的纳米结构中，边缘态的自旋流也可以被夹层所诱导的反铁磁交换场增强。应力可以产生比较大的赝磁场，从而调控石墨烯中拓扑界面网络的输运性质。石墨烯锯齿形边缘的自发磁化对拓扑相和边缘态产生影响，会影响器件设计的参数。另一部分研究针对光场对二维材料的调控。在光场的周期驱动下，能谷偏置狄拉克半金属表现出特异的行为，锯齿型纳米带的边缘态具有单向自旋流。二维反铁磁正方晶格会从拓扑绝缘体被调控成陈绝缘体。考虑光子的动量转移之后，石墨烯中的拓扑边界态可以被选择性地激发，从而产生局域的自旋流。通过总结以上研究成果，我们凝练出一套光场调控二维材料的理论模拟方案，包括材料计算、理论建模和求解。该理论方案有助于自旋电子器件研究的推广。为了更好地表征二维材料，我们还研究了若干新型二维材料的声子模式和拉曼张量。数值计算得出拉曼张量可以与实验作对比，从而得知新型二维多层材料的结构特征。该项目帮助我们加深对多层二维材料的自旋电子特性的理解，有助于进一步开发基于二维材料的自旋电子器件和集成电路系统。