Defect-induced states, defect-induced phase transition and excitonic states in bent transition metal dichalcogenide (TMD) nanoribbons: density functional vs. many body theory

TL;DR

This study explores how defects and bending in WS2 nanoribbons influence their electronic and optical properties, revealing phase transitions and tunable excitonic states through advanced theoretical methods.

Contribution

It combines density functional theory and many-body GW-BSE calculations to analyze defect and bending effects in TMD nanoribbons, providing new insights into their phase transitions and excitonic behavior.

Findings

Defects induce semiconducting-to-metallic phase transitions.

Bending and defect position tune optical absorption spectra.

Diverse exciton states are revealed in defected nanoribbons.

Abstract

Two-dimensional (2D) transition metal dichalcogenide (TMD) materials have versatile electronic and optical properties. TMD nanoribbons show interesting properties due to reduced dimensionality, quantum confinement, and edge states. Tang et al. showed that the edge bands evolved with bending can tune the optical properties for various widths of TMD nanoribbons. Defects are commonly present in 2D TMD materials, and can dramatically change the material properties. In this following work, we investigate the interaction between the edge and the defect states in WS2 nanoribbons with line defects under different bending conditions, using density functional theory (DFT). We reveal interesting semiconducting-to-metallic phase transitions, suggesting potential applications in nano-electronics or molecular electronics. We also calculate the optical absorption of the nanoribbons with different defect positions with the many-body GW-BSE (Bethe-Salpeter equation) approach, revealing a tunable optical spectrum and diverse exciton states in the defected TMD nanoribbons.