Tuning the electronic structure and magnetic coupling in armchair B2S nanoribbons using strain and staggered sublattice potential

Abstract

Magnetically-doped two dimensional honeycomb lattices are potential candidates for application in future spintronic devices. Monolayer B2S has been recently unveiled as a desirable honeycomb monolayer with an anisotropic Dirac cone. Here, we investigate the carrier-mediated exchange coupling, known as Ruderman-Kittel-Kasuya-Yoshida (RKKY) interaction, between two magnetic impurity moments in armchair-terminated B2S nanoribbons in the presence of strain and staggered sublattice potential. By using an accurate tight-binding model for the band structure of B2S nanoribbons near the main energy gap, we firstly study the electronic properties of all infinitelength armchair B2S nanoribbons (ABSNRs), with different edges, in the presence of both strain and staggered potential.It is found that the ABSNRs show different electronic and magnetic behaviors due to different edge morphologies. The band gap energy of ABSNRs depends strongly upon the applied staggered potential ∆ and thus one can engineer the electronic properties of the ABSNRs via tuning the external staggered potential. A complete and fully reversible semiconductor (or insulator) to metal transition has been observed via tuning the external staggered potential, which can be easily realized experimentally. A prominent feature is the presence of a quasiflat edge mode, isolated from the bulk modes in the ABSNRs belong to the family M = 6p, with M the width of the ABSNR and p an integer number. As a key feature, the position of the quasi-flatbands in the energy diagram of ABSNRs can be shifted by applying the in-plane strains εx and εy. At a critical staggered potential (∆c ∼ 0.5 eV), for nanoribbons of arbitrary width, the quasi-flatband changes to a perfect flatband.The RKKY interaction has an oscillating behaviour in terms of the applied staggered potentials, such that for two magnetic adatoms randomly distributed on the surface of an ABSNR the staggered potential can reverse the RKKY from antiferromagnetism to ferromagnetism and vice versa. The RKKY in terms of the width of the ribbon has also an oscillatory behavior. It is shown that the magnetic interactions between adsorbed magnetic impurities in ABSNRs can be manipulated by careful engineering of external staggered potential. Our findings pave the way for applications in spintronics and pseudospin electronics devices based on ABSNRs. arXiv:1906.10581v1 [cond-mat.mes-hall]