Spin relaxation in graphene nanoribbons in the presence of substrate surface roughness

Abstract

In this work spin transport in corrugated armchair graphene nanoribbons (AGNR) is studied. We survey combined effects of spin-orbit interaction and surface roughness, employing the nonequilibrium Green's function formalism and four orbitals tight-binding model. We modify hopping parameters regarding bending and distance of corrugated carbon atoms. The effects of surface roughness parameters, such as roughness amplitude and correlation length, on the spin transport of the graphene nanoribbons are studied. We show that increasing surface roughness amplitude breaks the AGNR symmetry and hybridize σ and π orbitals, leading to more spin flipping and therefore decrease in polarization. Unlike the roughness amplitude, the longer correlation length makes AGNR surface smoother and increases polarization. Moreover, Spin diffusion length of carriers is extracted and its dependency on the roughness parameters is investigated. We find the spin diffusion length for various surface corrugation amplitude in order of 1 to 80 micrometer .PACS numbers:

Spin Transport in Armchair Silicene Nanoribbon on the Substrate: The Role of Charged Impurity

“…Polarization is obtained by using Equation . Polarization decays with length as: where λ s is spin diffusion length (SDL) . Polarization is studied as a function of length, then SDL is extracted with an exponential fitting.…”

“…Polarization decays with length as: P L ð Þ ¼ P 0 exp ÀL=λ s ð Þ where λ s is spin diffusion length (SDL). [35] Polarization is studied as a function of length, then SDL is extracted with an exponential fitting. SDL for electron in the conduction band versus δU is plotted in the Figure 4(c).…”

“…[33,34] In this paper, we explore electric and spin transport in an armchair silicene nanoribbon under charged impurity. In our previous works, spin transport at the presence of surface roughness in graphene nanoribbon [35] and MoS2 and WS2 [36] were studied. It was shown that surface roughness has a high impact on the spin-flip for both materials.…”

Ab initio modelling of spin relaxation lengths in disordered graphene nanoribbons

“…Note that this effect follows an opposite trend to the one observed by Chaghazardi et al in AGNRs. [31] We argue that such discrepancy might be related to the fact that the authors studied nanoribbons whose lengths are smaller than 100 nm.…”

“…[33] Theoretically, Chaghazardi et al, using a tight-binding model studied an armchair GNR (tens of nanometers in length) in the presence of surface roughness, estimating spin-diffusion lengths ranging from 2 µm to 300 µm, which corresponds to spin-lifetimes on the order of nanoseconds. [31] Moreover, Salimath and Ghosh, performed Monte-Carlo simulations of long armchair GNRs (≈ 5 µm length), finding spin-relaxation lengths on the order of 1 − 4 micrometers. [35] As these calculations were performed on model Hamiltonians, this collection of results clearly suggest the need of firstprinciples studies to elucidate key mechanisms regarding spin-diffusion lengths in armchair GNRs (AGNR).…”