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It has been shown that intrinsic properties alone cannot sustain long lived spin signals in transition metal dichalcogenides (TMDs) and that these must come from extrinsic properties[1]. Here defects play a crucial role by enriching the optical properties of a material. In this work we link different types of defects to specific optical signatures by employing many-body perturbation theory with the Yambo package to obtain the optical absorption spectra of defected TMDs.
We find that the largely unstudied metal vacancies show a larger set of polarized excitons than chalcogen vacancies, introducing localized excitons in the sub-optical-gap region[2] whose wave functions and spectra make them good candidates as quantum emitters. However, when dealing with substitutional defects, the spin texture and pristine exciton energies are preserved, despite the strong interaction with the defect. Still, as the full optical-gap region remains free, these defects can be used as sites for grafting and patterning in optical detectors. A redistribution of excitonic weight between the A and B excitons is visible in both cases and may allow the quantification of the defect concentration. This work establishes excitonic signatures to characterize defects in 2D materials and highlights vacancies as qubit candidates for quantum computing.
[1] M. Ersfeld, F. Volmer, P. Melo, et al, Nano Lett. 2019, 19, 4083
[2] P. Melo, Z. Zanolli, M. Verstraete, Adv. Quantum Technol. 2021, 4: 2000118
