Effect of the edge states on the conductance and thermopower in Zigzag Phosphorene Nanoribbons

TL;DR

This study investigates how edge states influence conductance and thermopower in zigzag phosphorene nanoribbons, demonstrating tunable electronic properties via bias voltage and boundary potentials, with implications for thermoelectric applications.

Contribution

It introduces a numerical analysis of edge state effects on conductance and thermopower modulation in ZPNRs using tight-binding and scattering-matrix methods.

Findings

Bias voltage splits degenerate edge bands, switching conductance off.

Adjusting boundary potentials alters edge bands and enhances thermopower.

A zero-conductance plateau and increased thermopower are observed due to bulk energy gap formation.

Abstract

We numerically study the effect of the edge states on the conductance and thermopower in zigzag phosphorene nanoribbons (ZPNRs) based on the tight-binding model and the scattering-matrix method. It is interesting to find that the band dispersion, conductance, and thermopower can be modulated by applying a bias voltage and boundary potentials to the two layers of the ZPNRs. Under the certain bias voltage, the two-fold degenerate quasi-flat edge bands split perfectly. The conductance can be switched off, and the thermopower around zero energy increases. In addition, when only the boundary potential of the top layer or bottom layer is adjusted, only one edge band bends and merges into the bulk band. The first conductance plateau is strongly decreased to $e^2/h$ around zero energy. Particularly, when the two boundary potentials are adjusted, all the edge bands bend and fully merge into the bulk band, and the bulk energy gap is maximized. More interestingly, a pronounced conductance plateau with $G=0$ is found around zero energy, which is attributable to the opening of the bulk energy gap between the valence and conduction bands. Meanwhile, the thermopower can be enhanced more than twice, compared to that of the perfect ZPNRs. The large magnitude of thermopower is ascribed to the appearance of the bulk energy gap around zero energy. Our results show that the modulated ZPNRs are more reliable in thermoelectric application.