Quantum transport through the edge states of Zigzag phosphorene nanoribbons in presence of a single point defect: analytic Green's function method

TL;DR

This paper analytically investigates how a single point defect affects electronic transport along the edge states of zigzag phosphorene nanoribbons, revealing sensitivity to defect location and robustness of low-energy states.

Contribution

It provides analytical expressions for Green's functions and transmission in defective zigzag phosphorene nanoribbons, highlighting the impact of impurity position on edge state transport.

Findings

Transmission is suppressed when impurity is on the outermost edge site.

Low-energy states are robust against impurities moved away from the edge.

Analytical results agree with numerical Landauer transport calculations.

Abstract

Zigzag phosphorene nanoribbons have quasi-flat band edge modes entirely detached from the bulk states. We analytically study the electronic transport through such edge states in the presence of a localized defect for semi-infinite and finite ribbons. Using the tight-binding model, we derive analytical expressions for the Green's function and transmission amplitude of both pristine and defective nanoribbons. We find that the transmission of both semi-infinite and finite ribbons is sensitive to the location of a single impurity defect with respect to the edge. By the presence of an impurity on the outermost edge site of the ribbon, the transmission through the edge channel, similar to a one-dimensional chain, strongly suppresses for the entire energy spectrum of the quasi-flat band. In contrast, the transmission of low-energy $(E\approx 0)$ states, is robust as the impurity is moved one position far away from the edge on the same sub-lattice. The analytical calculations are also complemented by exact numerical transport computations using the Landauer approach.