化学吸附对单层和双层石墨烯电子结构及输运性质的影响

Graphene is two dimensional material with perfect electrical properties. Adatoms that are covalently bonded to graphene strongly perturb the electron structure of graphene and thus maybe expected to create resonant states in the vicinity of the Dirac point. These resonant states induce strong scattering for electrons in the graphene. This project focus on studying how the resonant scattering affect electronic structure and quantum transport properties in single layer and bilayer graphene. With the help of our well-developed Lanczos method, we can calculate the spectral function or density of states in momentum space accurately. Through the analysis of spectral function, we can obtain the effective energy dispersion of the adsorbate graphene. Gap-opening near the Dirac point induced by adatoms can be also clarified,which is very important for its future application in electronics. Moreover, we will study the localization of the impurity states in the gap and their effect on the transport and optical properties based on the one-parameter scaling hypothesis and exact diagonalization method.

石墨烯表面的化学吸附原子将会在狄拉克点附近形成共振能级，由此带来的共振散射将会对石墨烯的电子结构产生很大的修正。本项目旨在研究化学吸附基团，如氢基、甲基等，对表面吸附的单层和双层石墨烯的电子结构和量子输运性质的影响。利用我们发展完善的的Lanczos计算方法，通过大规模数值模拟计算体系准粒子谱函数。由此，我们可以准确的得到体系的准粒子能量色散关系，进而研究共振散射是如何在狄拉克点附近打开能隙的机制，这一能隙为其将来在电子学上的应用具有极为重要的意义。此外，我们将结合单参数标度理论和实空间严格对角化的方法，分析能隙中杂质电子态的局域化行为以及其对输运性质和光电性质的影响。

本项目以氢化的单层和双层石墨体系为研究对象，开展了相关的共振杂质效应的研究工作。在紧束缚近似的框架下，利用改进的Lancozs方法,系统研究了吸附原子对单层和双层石墨烯电子结构的影响,通过构造出其动量空间格林函数,模拟得到受杂质调控的色散关系，发现了吸附氢原子将狄拉克点劈裂产生能隙，且能隙大小和杂质浓度平方根成正比。这一能隙产生机制是由吸附杂质的多重共振散射导致的。此外，输运性质的计算结果也表明，可以通过调控杂质浓度实现石墨烯体系中的半金属绝缘体的转变，这一机制对其将来在电子学上的应用具有重要的意义。