Long-Range Effects in Topologically Defective Arm-Chair Graphene Nanoribbons

Area of Science:

• Condensed Matter Physics
• Materials Science
• Computational Chemistry

Background:

• 7/9-AGNR superlattices exhibit unique electronic properties influenced by their structure.
• Understanding their electronic band structure is crucial for potential applications.

Purpose of the Study:

• To investigate the electronic structure of 7/9-AGNR superlattices.
• To compare results from Density Functional Theory (DFT) with two model Hamiltonians (Hubbard and PPP).
• To resolve discrepancies between theoretical models and ab initio calculations.

Main Methods:

• Density Functional Theory (DFT) calculations.
• Hubbard (Hu) and Pariser-Parr-Pople (PPP) model Hamiltonians with mean-field approximation.
• Analysis of topological states and screened long-range interactions.

Main Results:

• Both Hu and PPP models predict a diminishing band gap with increasing superlattice size.
• DFT results show similar trends but with quantitative differences compared to the models.
• A screened long-range interaction model with an adjusted cutoff (λ=2) successfully reproduces DFT results.

Conclusions:

• Spin non-polarized solutions better describe 7/9 interfaces at the mean-field level.
• Accurate electronic structure requires long-range interactions beyond the Hubbard model.
• Screened long-range interactions are essential for reconciling model Hamiltonians with DFT for 7/9-AGNR superlattices.