Investigation on optical properties of bilayer graphene nanoribbons

Abstract

Using density functional theory, we investigate optical properties of $$\upalpha $$ and $$\upbeta $$ configuration of zigzag and armchair bilayer graphene nanoribbons. We demonstrate that depending on the width and edge symmetries, bilayer graphene nanoribbons could show various optical absorption spectra. These absorption spectra obey different rules. We show that these rules are based on parities of origin and destination wave functions that contribute in the optical absorption. In longitudinal polarization, the inter sub-band transitions occur when the contributed wave functions have different parities. However, in transverse direction, transitions existing between the same parities. This rule is followed by zigzag bilayer graphene nanoribbons. We check these rules for spin interactions and similar characteristic was observed. On the other hand, armchair bilayer graphene nanoribbons, based on width symmetry show either similar characteristic to zigzag or possessing mono frequency spectrum. In addition, $$\upalpha $$ configuration has slightly wider absorption region than $$\upbeta $$ ones. However, both show almost similar behavior in 1–2.47 $$\upmu $$ m region. These characteristics could be used as a tool in experimental investigations to scrutinize edge properties of samples.