圖樣化缺陷/吸附原子和與電磁場對石墨烯電子與傳輸之效應

Abstract

這個計畫的目標是探討在單層石墨烯中，藉缺陷、吸附原子、外加電磁場所產生的電子態和/或共振態。我們將會尋找可能的共振態以及它們和pseudospin或valley-sensitive過程有連結的的物理性質，同時將會提出調控這些共振態的傳輸特徵(Fano profile)以及pseudospin空間分布的方法。我們將會尋找一些特徵，像是在時變穿透率中的遽降結構(dip structures)，其產生原因是與一個圓偏振電磁場入射這系統時打開的能隙有關。 對於在單層石墨烯上缺陷和吸附原子的效應，我們有兩方面的目標。第一，我們計畫詳細的研究一些由於缺陷或吸附原子所引起的共振態，並研究這共振態與開放邊界(open-boundary)、edge-potential、及缺陷或吸附原子之間的關係。我們對扶椅型(armchair)的開放邊界特別有興趣，是由於我們最近發現邊緣位能(edge-potential)可以產生有色散(dispersive)的邊緣態有關。第二，我們計畫研究缺陷或吸附原子晶格圖案(lattice-patterned)的能帶結構。 對於在單層石墨烯外加電磁場的效應，我們將利用緊束縛模型，發展時變傳輸問題的計算方法。它提供了我們一個自然的架構，來探討以下的議題：(1) 低和高的入射能量(2) 能帶變形(warping effects) (3) 時變位能方向性(orientation)的效應(4) 能谷間(inter-valley)與能谷內(intra-valley)躍遷過程. 此時變調整的傳輸，包含時變位能、線性偏振以及圓偏振的電磁場之間的互相影響。另外，靜態位能與以上各時變物理量之間的交互作用也會被探討。

Title of the proposal: Patterned adsorbates and Electromagnetic field effects on electron states and transport in graphene This proposal aims at exploring electronics states and/or resonant states in graphene produced by defects, adsorbate atoms, and external electromagnetic fields. We will look for possible resonant states and their physical nature in their connection to pseudospin- or valley-sensitive processes. We will propose ways to monitor these resonant states in transport characteristics (Fano profile) and pseudospin spatial distribution. We will look for signatures, such as dip structures in time-dependent transport, for the gap-opening when a circularly polarized electromagnetic field incident upon the system. For the effects of defects and adsorbates on graphene, our targets are two folded. First, we plan to study in detail the resonant states arise from a few defect or adsorbates. The interplay with the open boundary and the further effects of edge-potential on these resonant states will be explored. Of particular interest is an armchair open boundary, because of our recent result on the generation of a dispersive edge state by an edge-potential. Second, we plan to study lattice-patterned defects or adsorbates and the energy bands. For the effects of external electromagnetic fields on graphene, we will formulate the time-dependent transmission problem in the tight-binding model. This provides us a natural framework for the exploration of (1) both low and high incident energies, (2) warping effects, (3) effects of the orientation of the time-modulated region, and (4) the inter- and intra-valley processes. The time-modulation includes time-modulated potential, and linearly- and circularly-polarized electromagnetic fields. Interplay between a static potential and the time-modulated agents will also be explored.