Strain effect on quantum conductance of graphene nanoribbons from maximally localized Wannier functions

Abstract

Density-functional study of strain effects on the electronic band structure and transport properties of the graphene nanoribbons (GNR) is presented. We apply a uniaxial strain $(\ensuremath{\epsilon})$ in the $x$ (nearest-neighbor) and $y$ (second-nearest-neighbor) directions, related to the deformation of zigzag- and armchair-edge GNRs (AGNR and ZGNR), respectively. We calculate the quantum conductance and band structures of the GNR using the Wannier function in a strain range from $\ensuremath{-}8\mathrm{%}$ to $+8\mathrm{%}$ (minus and plus signs show compression and tensile strain). As strain increases, depending on the AGNR family type, the electrical conductivity changes from an insulator to a conductor. This is accompanied by a variation in the electron and hole effective masses. The compression ${\ensuremath{\epsilon}}_{x}$ in ZGNR shifts some bands to below the Fermi level $({E}_{f})$ and the quantum conductance does not change but the tensile ${\ensuremath{\epsilon}}_{x}$ causes an increase in the quantum conductance to $10{e}^{2}/h$ near the ${E}_{f}$. For transverse direction, it is very sensitive to strain and the tensile ${\ensuremath{\epsilon}}_{y}$ causes an increase in the conductance while the compressive ${\ensuremath{\epsilon}}_{y}$ decreases the conductance at first but increases it later.