Nonlinear Properties of Monolayer Transition Metal Dichalcogenide Systems

The second-order nonlinear optical properties of monolayer transition metal dichalcogenides (TMDs) have been drawing increased interest for device applications, yet, challenges remain in the measurements of their nonlinear responses. In this work, we report a first-principles analysis of the second-order nonlinear optical response of monolayer TMDs (group V and VI) in their hexagonal form and as hexagonal Janus TMDs. These calculations are useful for benchmarking and understanding trends across different TMD compositions. We compare to experimental measurements when available and find that the nonlinear optical properties of these materials are comparable to other bulk materials currently used in electro-optical devices. Given the magnitude of the second-order nonlinear optical properties and the two-dimensional nature of these materials, avenues are opening for reducing the size of electro-optical devices by using monolayer TMDs.