Band Gap of Strained Graphene Nanoribbons

TL;DR

This paper investigates how different types of mechanical strain affect the electronic band gap of graphene nanoribbons, revealing that edge shape and strain type significantly influence their electronic properties.

Contribution

It provides a detailed analysis of strain effects on GNRs' band gaps, including a simple analytical model for armchair GNRs, highlighting the dependence on edge shape and strain type.

Findings

Uniaxial strain causes linear or oscillatory band gap changes in armchair GNRs.

Shear strain tends to decrease the band gap.

Strain influences spin polarization and band gap in zigzag GNRs.

Abstract

The band structures of strained graphene nanoribbons (GNRs) are examined by a tight binding Hamiltonian that is directly related to the type and strength of strains. Compared to the two-dimensional graphene whose band gap remains close to zero even if a large strain is applied, the band gap of graphene nanoribbon (GNR) is sensitive to both uniaxial and shears strains. The effect of strain on the electronic structure of a GNR strongly depends on its edge shape and structural indices. For an armchair GNR, uniaxial weak strain changes the band gap in a linear fashion, and for a large strain, it results in periodic oscillation of the band gap. On the other hand, shear strain always tend to reduce the band gap. For a zigzag GNR, the effect of strain is to change the spin polarization at the edges of GNR, thereby modulate the band gap. A simple analytical model is proposed to interpret the band gap responds to strain in armchair GNR, which agrees with the numerical results.