Effects of zigzag edge states on the thermoelectric properties of finite graphene nanoribbons

TL;DR

This paper investigates how zigzag edge states influence the thermoelectric properties of finite graphene nanoribbons, revealing edge state transport conditions, behavior with armchair edges, and robustness against defects.

Contribution

It introduces a theoretical analysis of edge state effects on thermoelectric performance in finite GNRs, highlighting the role of edge coupling and defect resilience.

Findings

Edge states enable electron transport only if channel length is short enough.

Thermoelectric behavior linked to mid-gap states in semiconducting GNRs.

Zigzag edge state conductance is robust against defects.

Abstract

Thermoelectric properties of finite graphene nanoribbons (GNRs) coupled to metallic electrodes are theoretically studied in the framework of tight-binding model and Green's function approach. When the zigzag sides are coupled to the electrodes, the electron transport through the localized edge states can occur only if the channel length between electrodes is smaller than the decay length of these localized zigzag edge states. When the armchair edges are coupled to the electrodes, there is an interesting thermoelectric behavior associated with the mid-gap states when the GNR is in the semiconducting phase. Here we show that the thermoelectric behavior of zigzag edge states of GNRs with armchair sides connected to electrodes is similar to that of two parallel quantum dots with similar orbital degeneracy. Furthermore, it is demonstrated that the electrical conductance and power factor given by the zigzag edge states are quite robust against the defect scattering.