Electric Field Effects on Armchair MoS2 Nanoribbons

TL;DR

This study uses density functional theory to explore how external electric fields influence the electronic properties of armchair MoS2 nanoribbons, revealing tunable band-gaps and magnetic states relevant for nanoelectronics.

Contribution

It demonstrates that external electric fields can significantly modulate the band-gap and magnetic properties of MoS2 nanoribbons, including inducing a metal-insulator transition and changing the nature of the band-gap.

Findings

Electric field reduces the band-gap, causing a metal-insulator transition.

High density of states at Fermi level can induce ferromagnetism modulated by the electric field.

In bilayer nanoribbons, the band-gap can switch from indirect to direct under an external field.

Abstract

{\it Ab initio} density functional theory calculations are performed to investigate the electronic structure of MoS$_2$ armchair nanoribbons in the presence of an external static electric field. Such nanoribbons, which are nonmagnetic and semiconducting, exhibit a set of weakly interacting edge states whose energy position determines the band-gap of the system. We show that, by applying an external transverse electric field, $E_\mathrm{ext}$, the nanoribbons band-gap can be significantly reduced, leading to a metal-insulator transition beyond a certain critical value. Moreover, the presence of a sufficiently high density of states at the Fermi level in the vicinity of the metal-insulator transition leads to the onset of Stoner ferromagnetism that can be modulated, and even extinguished, by $E_\mathrm{ext}$. In the case of bi-layer nanoribbons we further show that the band-gap can be changed from indirect to direct by applying a transverse field, an effect which might be of significance for opto-electronics applications.