Effects of edge magnetism and external electric field on energy gaps in multilayer graphene nanoribbons

Abstract

Using first principles density functional theory, we study the electronic structure of multilayer graphene nanoribbons as a function of the ribbon width and the external electric field, applied perpendicular to the ribbon layers. We consider two types of edges (armchair and zigzag), each with two edge alignments (referred to as α-and β-alignments). We show that, as in monolayer and bilayer armchair nanoribbons, multilayer armchair nanoribbons exhibit three classes of energy gaps which decrease with increasing width. Non-magnetic multilayer zigzag nanoribbons have band structures that are sensitive to the edge alignments and the number of layers, indicating different magnetic properties and resulting energy gaps. We find that energy gaps can be induced in ABCstacked ribbons with an perpendicular external electric field, while in other stacking sequences, the gaps decrease or remain closed as the external electric field increases.

Band structure and optical absorption in multilayer armchair graphene nanoribbons: A Pariser-Parr-Pople model study

“…6a and 7 we present the PPP-RHF band structures of a few members of this family, 2-AGNR-11-α, 3-AGNR-8-α, 4-AGNR-8-α, and 10-AGNR-8-α, and from the figures it is obvious that all these ribbons have substantial band gaps. Therefore, we believe that the ab initio results of Sahu et al 13,20 reporting these systems as almost metallic, are due to the well-known tendency of the DFT to underestimate the gaps, and that a better estimate of the gap can only be made by some electron-correlated approach such as the GW approximation. 8 We investigate the effect of edge alignment on the band structure of bilayer AGNRs by presenting the band structure of 2-AGNR-11-α (Fig.6 (a)), and 2-AGNR-11-β (Fig.6(b)).…”

“…8 We expect the long-range e-e interactions, as incorporated in the PPP model, to play a similar role for multilayer AGNRs as well. According to the ab initio DFT calculations of Sahu et al 13,20 , all n-AGNR-N A -α, of the family N A = 3p + 2, exhibit much smaller gaps compared to the other families, suggesting a metal-like behavior. In Figs.…”

“…Based upon first principles DFT calculations Sahu et al, 13,20 discovered that for bilayer AGNRs, and other multilayer AGNRs E 3p+1…”

“…8 While numerous theoretical studies of the electronic structure and related properties of the mono-layer GNRs exist, 10 relatively fewer calculations on bilayer and multilayer-GNRs have been performed. [11][12][13][14][15][16][17][18][19][20] Recently, gated bilayer graphene has attracted a great deal of attention in the experimental, [21][22][23][24][25] as well as theoretical communities. [26][27][28][29][30] The energy gap in bilayer graphene, in the presence of a transverse electric field, has been found to be tunable over a wide range of values (up to 250 meV).…”

Electro-absorption of silicene and bilayer graphene quantum dots

“…The electronic properties of various graphene nanoribbon structures and the influence of the applied voltage are being studied both for the out-of-plane [16][17][18] and for the in-plane [19][20][21][22] field directions. The optical and magnetic properties of the single and multilayer graphene QDs of various shapes have also been studied at zero field.…”