Probing the edge states in a zigzag phosphorene nanoribbon via RKKY exchange interaction

TL;DR

This paper investigates how the RKKY exchange interaction reveals the unique edge states in zigzag phosphorene nanoribbons, showing how external tuning can isolate edge contributions and enhance interaction strength.

Contribution

It introduces a theoretical method to distinguish edge state effects in RKKY interactions in phosphorene nanoribbons, highlighting the influence of external gate voltage and strain.

Findings

Edge states cause rapid RKKY oscillations compared to bulk.

External gate voltage can isolate edge contributions in RKKY.

Strain and doping can enhance RKKY interaction strength.

Abstract

Phosphorene is an anisotropic puckered two-dimensional ($2$D) hexagonal lattice of phosphorus atoms. The edge modes in a zigzag phosphorene nanoribbon (ZPNR) are quasi-flat in nature and fully isolated from the bulk states, which are unique in comparison to the other hexagonal lattices like graphene, silicene etc. We theoretically investigate the Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction between two magnetic impurities placed on the nanoribbon, and extract the signatures of the flat edge states via the behavior of it. Due to the complete separation of the edge states from the bulk, we can isolate the edge mode contribution via the RKKY interaction from that of the bulk by tuning the external gate potential when both the impurities are placed at the same edge. The bulk induced RKKY interaction exhibits very smooth oscillation with the distance between the two impurities, whereas for edge modes it fluctuates very rapidly. We also explore the effect of tensile strain both in absence and presence of gate voltage and reveal that the RKKY interaction strength can be boosted under suitable doping, when both the impurities are within the bulk.