Dark-exciton based strain sensing in transition metal dichalcogenides

TL;DR

This paper proposes a novel strain sensing method using dark excitons in monolayer transition metal dichalcogenides, demonstrating high sensitivity through strain-controlled exciton behavior and photoluminescence changes.

Contribution

It introduces a new dark-exciton-based strain sensing concept leveraging exciton landscape control in 2D materials, with high optical gauge factors.

Findings

Dark exciton intensity changes significantly with minimal strain (0.05%)

Strain controls dark-bright exciton separation affecting photoluminescence

Optical gauge factors up to 8000 indicate high sensitivity

Abstract

The trend towards ever smaller high-performance devices in modern technology requires novel materials with new functionalities. The recent emergence of atomically thin two-dimensional (2D) materials has opened up possibilities for the design of ultra-thin and flexible nanoelectronic devices. As truly 2D materials, they exhibit an optimal surface-to-volume ratio, which results in an extremely high sensitivity to external changes. This makes these materials optimal candidates for sensing applications. Here, we exploit the remarkably diverse exciton landscape in monolayer transition metal dichalcogenides to propose a novel dark-exciton-based concept for ultra sensitive strain sensors. We demonstrate that the dark-bright-exciton separation can be controlled by strain, which has a crucial impact on the activation of dark excitonic states. This results in a pronounced intensity change of dark excitons in photoluminescence spectra, when only 0.05 $\%$ strain is applied. The predicted extremely high optical gauge factors of up to 8000 are promising for the design of optical strain sensors.