Developing a robust system with a strong tunable nonlinear second harmonic generation (SHG) is desirable. In this work, we calculateSHG arising from the excitonic states of monolayer molybdenum disulfide quantum dots (MoS2 QDs) with a parabolic confinement potential within massive Dirac fermion model using the density matrix formalism.Wetheoretically demonstrate that MoS2 QDs can exhibit a giant and tunable Spin-Valley dependent excitonic SHG, which can be tuned from 0 to ∼107 pm V−1 and realized by biasing nanostructured gates or by position-dependent doping. Remarkably, the strength of SHGresponse is more than two orders of magnitude higher than that in monolayer MoS2. Furthermore, robust excitonic effects together with strong spin-valley coupling in monolayer transition metal dichalcogenides quantum dots (TMDCQDs), which are tunable depending on the strength of the quantum confinement, make them as a promising candidate for ultrathin nonlinear optical materials with large nonlinearities.Webelieve that this study could spark interest in the nonlinear optical properties of TMDCQDs and open up a variety of new avenues for versatile novel 2D nonlinear photonics and optoelectronic nanodevices.
