On the technological side, we developed several new approaches to apply mechanical strain to 2D materials. We realized new approaches to apply either large uniforms strain or strongly spatially inhomogeneous strain at low temperate. These new techniques allowed us to explore previously unexplored regions of the phase space of strain-dependent physics in 2D materials and to discover multiple new phenomena. First, we discovered strain-related renormalization of mechanical constant (Young modulus, Poisson’s ratio, etc…) of 2D materials. We showed that 2D materials are more akin, mechanically, to soft matter studied in biology than to hard solids. Second, we showed that inhomogeneous strain field acts as a driving force on normally neutral excitons, electron/hole complexes induced by light in 2D semiconductors. We showed that in presence of this force neutral excitons are converted into charged excitons (Obj. 4,6). This discovery is critical for the operation of single quantum emitters based on 2D materials. Finally, we explored non-linear couplings between various vibrational modes in resonators based on 2D materials. We showed that this coupling leads to mode hybridization, nanomechanical squeezing, and upconversion. We showed these properties can be used to realize all-mechanical optical spectroscopic characterization of 2D materials.
To enable progress along these main directions, we had to improve the quality of 2D materials (2DMs) significantly. Specifically, we found approaches to characterize the presence of defects, and scattering channels, and improve the gating efficiency of 2DMs. Specifically, we demonstrated the use of excitonic resonance to characterize the presence of surface disorder, the effect of defects on spin transport across 2DM interfaces, showed the approach to generate record electric fields up to 3V/nm in a solid, and understood the effect of disorder on dielectric screening. The work was disseminated in scientific publications, press-releases, and popular articles.
