Emergence of one-dimensional wires of free carriers in transition-metal-dichalcogenide nanostructures

TL;DR

This paper demonstrates that transition-metal-dichalcogenide nanostructures naturally develop one-dimensional metallic wires at their edges or boundaries due to polar discontinuities, with controllable properties and broad application potential.

Contribution

It reveals the universal emergence of metallic states in TMD nanostructures driven by polar discontinuities, including at edges and inversion domain boundaries, and discusses their controllability.

Findings

Metallic states form at edges and boundaries of TMD nanostructures.

Free charge density increases with system size until complete screening.

Edge and boundary configurations can be manipulated to control metallic states.

Abstract

We highlight the emergence of metallic states in two-dimensional transition-metal-dichalcogenide nanostructures -nanoribbons, islands, and inversion domain boundaries- as a widespread and universal phenomenon driven by the polar discontinuities occurring at their edges or boundaries. We show that such metallic states form one-dimensional wires of electrons or holes, with a free charge density that increases with the system size, up to complete screening of the polarization charge, and can also be controlled by the specific edge or boundary configurations, e.g. through chemisorption of hydrogen or sulfur atoms at the edges. For triangular islands, local polar discontinuities occur even in the absence of a total dipole moment for the island and lead to an accumulation of free carriers close to the edges, providing a consistent explanation of previous experimental observations. To further stress the universal character of these mechanisms, we show that polar discontinuities give rise to metallic states also at inversion domain boundaries. These findings underscore the potential of engineering transition-metal-dichalcogenide nanostructures for manifold applications in nano- and opto-electronics, spintronics, catalysis, and solar-energy harvesting.