The ability to manipulate excitonic complexes in 2D materials is of fundamental importance for the development of excitonic-based optoelectronic devices operating in low-carrier density, low-power regimes. Correlating locally variable quantities with emission properties of excitonic complexes on a sub-diffraction length scale could enable on-demand control of the mutual conversion between excitons and trions. In particular, control over trion density upon photoexcitation in a functionalized 2D material disclose the possibility to achieve trionic optical gain, that is, a condition of optical gain sustained by the difference between trion and pre-doped electron density. As a peculiarity, trionic optical gain does not require global population inversion common to optical gain mechanisms of conventional semiconductors. Therefore, trion density control could enable optical amplification and lasing at unprecedented low levels of excitation. To this end, we aim to understand the photoexcitation-dependent trion formation process, their abundance and stability upon variation of local quantities such as carrier doping, defects density and strain fields in 2D materials. To pursue this goal we will implement a structural /spectroscopic correlated approach based on hyperspectral nanoimaging and far-field cryo-microscopy of 2D monolayers transferred on a plasmonic nanopillar array with controlled levels of charge doping and strain. Demonstration of trionic optical gain in such conditions will provide the necessary requirement for achieving trionic lasing. Laser feedback will be then realized by engineering the surface lattice resonance of a plasmonic nanopillar cavity to match the trionic peak gain wavelength.
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Inducing trionic gain in two-dimensional semiconductors by local strain and charge manipulation