節點吸附原子在金屬性扶手型帶狀石墨烯中的電子態

Abstract

一個節點吸附原子在金屬性扶手型帶狀石墨烯中會產生束縛態[1]，此束縛態在空間中的波函數展現了非均向衰退的行為。此外多個節點吸附原子也會產生與其對應的束縛態，我們對於探討此類束縛態空間波函數的分布非常感興趣。基於雙節點吸附原子系統的概念，我們建立了雙基底近似法，用以計算雙節點吸附原子束縛態的空間行為。雙基底近似中所述之基底為兩個節點吸附原子各自的束縛態。這個近似法使我們更加瞭解單節點吸附原子束縛態空間波函數之正負號的位置上，對在該位置之吸附原子束縛能的影響。此論文的重點是將節點吸附原子的次晶格種類、節點位置與判斷吸附原子的種類連結，以及節點吸附原子在導電率上的影響。同時我們發現在周期性的節點吸附原子中，其能帶結構與其周期中所包含的次晶格數量有關，但在這樣的系統中無能隙能帶的結構卻不受吸附原子的影響，而其他能隙能帶的結構會因此而調變。並且也拓展了基底近似法，用以描述長周期節點吸附原子的能帶結構。

An adsorbate located on a nodal site of a metallic armchair graphene nanoribbon (AGNR) forms a bound state [1]. The bound state wave function exhibits anisotropic decaying behavior. It is then of interest to explore the effect of this spatial behavior on the bound state that will form between two or more nodal adsorbates. Specifically, we consider the case of two nodal adsorbates for the establishment of a two-basis approximation (2BA) in the calculation of the bound states formed from the nodal adsorbate pair. The two basis are the bound state wave function of the individual nodal adsorbate. This 2BA scheme provides us a transparent way to understand the bound state energy of the nodal adsorbate pair in light of the site-dependent sign of the basis wave function. Issues concerning the A/B-type and the nodal-type of the 2 adsorbates and the connection to adsorbate recognition will be studied. Effects on the conductance will also be studied. Furthermore, cases of nodal adsorbate chain, with nodal adsorbates line up periodically along a nodal line of the AGNR, are studied. Depending on whether only the A (or B) site or both A and B sites involved in the nodal adsorbate chain, one or two dispersive energy bands, respectively, are formed in the energy of the AGNR gapless sub-band. Interestingly, the gapless sub-band remain intact but the gapped sub-bands are modified by the presence of the nodal-adsorbate chain. Our two-basis approximation is extended to describe nodal-adsorbate chain energy band of large enough adsorbate separation.