Valley polarized current and resonant electronic transport in a non-uniform $\mathbf{MoS}_2$ zigzag nanoribbon

TL;DR

This study investigates valley-polarized electronic transport in non-uniform MoS2 zigzag nanoribbons, revealing resonant conductance, valley Hall effects, and near-complete valley polarization achievable through local gating.

Contribution

It demonstrates how spatial potential variations induce valley polarization and resonant transport phenomena in MoS2 nanoribbons, advancing valleytronics understanding.

Findings

Sharp conductance resonances due to n-p-n junctions

Edge current blocking in gated wires despite metallic bands

Valley polarization of current via local gating

Abstract

Using the tight-binding approach we study the electronic transport in a $\mathrm{MoS}_2$ zigzag ribbon with a spatially varying potential profile. Considering a ribbon with a smooth potential step in the Fermi energy regime where the transport is dominated by the edge modes, we find that the conductance exhibits sharp resonances due to the resonant transport through a n-p-n junction effectively created in the structure. We show that in a gated wire the current carried on the wire edges can be blocked despite the metallic band structure of the ribbon. For the Fermi energies corresponding to $\mathrm{MoS}_2$ bulk conduction band, we identify states of the semi-infinite wire that are polarized in the $K$, $K'$, $Q$ valleys and exhibit the valley Hall effect distinctly visible in a nonuniform ribbon. Finally, we show that well-defined momenta of the valley polarized modes allow nearly complete valley polarization of the current in a locally gated ribbon.