Abstract
Monolayer transition metal dichalcogenides have recently attracted great interests because the quantum dots embedded in monolayer can serve as optically active single-photon emitters. Here, we provide an interpretation of the recombination mechanisms of these quantum emitters through polarization-resolved and magneto-optical spectroscopy at low temperature. Three types of defect-related quantum emitters in monolayer tungsten diselenide (WSe2) are observed, with different exciton g-factors of 2.02, 9.36, and unobservable Zeeman shift, respectively. The various magnetic response of the spatially localized excitons strongly indicate that the radiative recombination stems from the different transitions between defect-induced energy levels, valance, and conduction bands. Furthermore, the different g-factors and zero-field splittings of the three types of emitters strongly show that quantum dots embedded in monolayer have various types of confining potentials for localized excitons, resulting in electron–hole exchange interaction with a range of values in the presence of anisotropy. Our work further sheds light on the recombination mechanisms of defect-related quantum emitters and paves a way toward understanding the role of defects in single-photon emitters in atomically thin semiconductors.
Highlights
It has been discovered that a single-layer Transition metal dichalcogenides (TMD) can be used as a host material for single quantum emitters[6,7,8,9,10,11,12] at low temperature, which provides a new platform to develop on-chip integrated single-photon source and quantum information processing
The spin does not contribute to Zeeman splitting because the optical valley selection rule requires that the valence and conduction band have the same spin
The valley magnetic moment associated with the Berry curvature does not contribute to Zeeman splitting in TMD monolayer.[31,36]
Summary
Transition metal dichalcogenides (TMD) monolayers have raised great attentions due to their strong spin–orbit coupling, large exciton binding energy, and direct bandgap in the visible region.[1,2,3,4,5] Recently, it has been discovered that a single-layer TMD can be used as a host material for single quantum emitters[6,7,8,9,10,11,12] at low temperature, which provides a new platform to develop on-chip integrated single-photon source and quantum information processing. The origin of the 2D host of quantum emitters is still vague
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