Spin Transport in Bilayer Graphene Armchair Nanoribbon: A Monte Carlo Simulation Study

In this paper, we study the spin relaxation in bilayer armchair graphene nanoribbons (acGNRs) by employing the semiclassical Monte Carlo approach. D'yakonov-Perel relaxation due to structural inversion asymmetry (Rashba spin-orbit coupling) and Elliott-Yafet relaxation cause spin dephasing in bilayer GNRs. We investigate the spin relaxation in bilayer alpha-, beta-, and gamma-acGNRs with varying their width and the temperature. We consider injection polarization along the z-direction, which is perpendicular to the plane of grapheme, and study the magnitude of ensemble-averaged spin variation along the x-direction which is the transport direction. To the best of our knowledge, there has been no Monte Carlo simulation performed on spin transport in acGNRs. We investigate the role of various scattering events in spin relaxation in bilayer acGNRs. We find that the spin relaxation length in the alpha-acGNR is 6.5% higher than in beta-acGNR and 10.8% higher than in gamma-acGNR at 300 K. We also report the results of the variation of spin relaxation length with varying temperatures. We find that the spin relaxation length decreases by 9% in alpha-acGNR, by 10.5% in beta-acGNR, and 11% in gamma-ac GNR at 300 K compared to 4 K. The decrease in spin relaxation length at the higher temperature is due to the increase in phonon and spin-flip scattering rates at the higher temperature. This theoretical investigation is particularly important to identify the factors responsible for the experimentally observed spin relaxation length in GNRs.