基于石墨烯的量子纳米体系表面等离激元特性与激发方式的理论研究

The surface plasmon in graphene (with the size smaller than 10 nm) possesses unique properties such as broad frequency band, long lifetime and enabled control due to the quantum finite-size effect, which makes it great potential value in the application for focusing, particle trapping, absorption, biosensor, and cancer therapy at molecular scale. The surface plasmon in graphene can interact with photon, phonon and electron, and generates many marvelous physical phenomena. The surface plasmon in graphene is also a complex platform for the exploration of many-body physics. So the investigation on it has great scientific significance. Hence, it is necessary to investigate theoretically the plasmon excitation, band broadening and controlling method by using a fully quantum-mechanical method. In this project, the surface plasmon of graphene nanosystems with both stacked and planar structure will be investigated,and the hybrid structure of nanographene with metal nanowire and metal nanotube will be studied also. The quantum methods used include time-dependent density functional theory (TDDFT),many-body Green function(GW) and quantum Monte Carlo method(QMC).We will present benchmark data for the theoretical study of surface plasmon after careful checking the results obtained from using different methods.In addition, the plasmon properties especially the coupling property between graphene quantum monomer will be studied also, which can be influenced by geometry, size, edge, doping, distance between the dots and polarization direction of light. For the low energy electron moving atop the graphene, we will study the dynamic process of the electron excitation in the graphene, and the characteristic of surface plasmon, using the time-dependent density functional theory in the real-time-propagation (RTP) approach, and we try to grasp the physical nature in it. Similarly, the excited situation for surface sound wave assisted will be studied. The micro-dynamic picture of surface plasmon excitation and local field enhancement under the interaction of low energy moving electron or surface acoustic wave will be obtained. These results would provide useful information for nano-scale graphene plasmon device.

尺度10纳米以下石墨烯中表面等离激元在分子尺度的聚焦、粒子捕获、吸收、生物传感和疾病治疗等方面有巨大应用价值，它可以和光子、声子以及电子发生相互作用产生新奇丰富的物理现象，对其研究具有重要科学意义。在微观物理机制、波段扩展和调控方式等方面亟需在全量子水平上对其开展理论研究。本项目采用含时密度泛函理论、多体格林函数以及量子Monte Carlo等研究石墨烯量子纳米体系的等离激元特性，为等离激元研究提供基准性数据。研究体系包含平面型和层叠型石墨烯构成的阵列及其和金属纳米线、管等组成的复合结构，考虑形状、尺寸、边缘、掺杂、间距、排列方式以及激发场偏振方向等影响。采用含时密度泛函框架下的实时传播子方法研究低能运动电子激发以及表面声波辅助光激发两种激发方式下石墨烯中的电子激发动力学和等离激元性质，建立特定激发方式下局域场增强的微观动力学图象，为优化设计不同应用背景下的纳米等离激元器件提供理论指导。

本课题主要研究内容：.1）在理论上对尺度在10纳米以下的石墨烯及其构成的多种特征结构的表面等离激元特性进行了系统研究。该尺度在众多领域有重要应用价值，且量子受限效应和边界状态影响明显，其特性与大尺度石墨烯有很大的区别并具有丰富的物理现象。.2）基于含时密度泛函理论方法研究石墨烯阵列中各单体之间的等离激元及耦合效应。通过设计不同图案的石墨烯或石墨烯孔洞型阵列，分析形状、尺寸、缺陷、边缘、掺杂、间距、排列方式以及激发场的偏振方向等对等离激元以及耦合特性的影响。和宏观大小材料相比，纳米结构的等离激元具有一些不同的特征，在低能共振区，光谱线发生展宽，并且发生劈裂。.3）探究掺杂石墨烯量子点中表面等离激元特性。通过氮、硫、硼等掺杂石墨烯量子点能够实现对体系等离激元性能的调控，并探究掺杂浓度、掺杂方式等对表面等离激元共振模式的调控以及对空间局域场增强效应的影响。实现了石墨烯等离激元的共振频率从中红外区域到太赫兹频段的可调，极大拓宽了作用范围。.利用不同衬底对石墨烯量子纳米系统中表面等离激元进行调控。研究不同金属衬底对石墨烯及其构成的多种特征结构中表面等离激元共振模式的影响，以及衬底对等离激元耦合和局域场增强效应的影响。通过贵金属膜的调节，等离激元主峰的能量共振移动到可见光区域。.4）对其它类石墨烯的二维平面纳米结构的表面等离激元进行探究。分别研究了磷烯、BC3、C2O、Si2BN等体系的等离激元特性，表现出了异于石墨烯纳米结构的独特性能。.5）研究了运动电荷在石墨烯中的电子激发动力学行为及等离激元特征。另外，分析在表面声波和激发光的共同作用下石墨烯中电子激发的本质性变化及其对表面等离激元的调控规律。. 项目针对石墨烯量子纳米结构的表面等离激元特性进行了系统研究，并探究了外界条件（性状、尺寸、掺杂、间距等）对体系等离激元性能的影响，在国内外重要刊物上发表了一系列有一定影响的论文，举办了重要学术会议，研究工作得到国内外同行的认同。