Theory of epitaxial graphene

外延石墨烯技术的快速发展为石墨烯性质的可控修饰和新型石墨烯结构的设计开辟了广阔的前景。这些结构包括不同碳化硅小面上的石墨烯外延层和不同的碳化硅多晶型，通过外来原子嵌入到碳化硅-石墨烯界面获得准独立的石墨烯，以及丰富的多层石墨烯，特别是旋转断层石墨烯多层膜。目前，对这些系统的理论理解还远远不完整。即使对于研究最深入的体系，碳化硅表面和碳端面上的石墨烯，也有许多特征有待解释，而石墨烯在高指数碳化硅小面和非极性表面上的性质在理论上仍未被探索。在这个方案中，我们旨在详细了解这些系统，包括界面态的作用，衬底刻面选择的作用，外延层和多层膜中磁性和非磁性杂质的性质，以及石墨烯-碳化硅界面的电子和振动特性。值得注意的是，旋转断层石墨烯多层膜的非常丰富和新颖的物理学将被研究，特别是电子在小角度的局域化，输运现象，和声子谱。我们将使用从头算密度泛函方法和为基于石墨烯的体系量身定做的有效紧束缚方法，以及基于适当修改的狄拉克-魏哈密顿量的分析模型。

The rapid progress of epitaxial graphene technology has opened a wide vista of new methods for the controllable modification of graphene properties and the design of novel graphene-based structures. These structures include graphene epitaxial layers on various SiC facets and various SiC polytypes, quasi-freestanding graphene obtained by foreign atom intercalation into the SiC-graphene interface, and a rich variety of multilayer graphenes, in particular rotationally faulted graphene multilayers. Theoretical understanding of these systems is, at present, far from complete. Even for the most intensively studied systems, graphene on the Si- and C- terminated faces of SiC, many features await explanation, whereas the properties of graphene on the high-indexed SiC facets and on the non-polar surfaces remain theoretically unexplored. In this proposal, we aim at a detailed understanding of these systems including the role of the interface states, the role of the substrate facet choice, the properties of magnetic and non-magnetic impurities in both epilayers and multilayers, and the electronic and vibrational characteristics of the graphene-SiC interface. Notably, a very rich and novel physics of rotationally faulted graphene multilayers will be studied, in particular the electron localization at small angles, transport phenomena, and the phonon spectrum. We shall employ ab-initio DFT methods in combination with an efficient tight-binding approach tailored for graphene-based systems, as well as analytical models based on appropriately modified Dirac-Weil Hamiltonians.