Theory of the CH$_\text{S}^-$ Defect in MoS$_2$ Confirming the Origin of the Quantum Emission

Abstract:Establishing the microscopic origin of localized emission in two-dimensional materials through consistent agreement between experiment and theory remains challenging. Recent STM/STS-STML measurements assigned an emission near 1.8 eV in monolayer MoS$_2$/hBN(2L)/graphene to the negatively charged CH$_\mathrm{S}^{-}$ defect. However, a comprehensive theoretical description of this emitter is still lacking. Here, we develop such a description and systematically investigate the photophysical properties of CH$_\mathrm{S}^{-}$ in monolayer MoS$_2$, two bilayer configurations, and a MoS$_2$/hBN heterostructure. The defect retains a similar local geometry and favors a singlet ground state in all four environments, whereas its electronic transition, zero-phonon line, electron-phonon coupling, radiative lifetime, and transition-dipole orientation depend strongly on the surrounding layers. The isolated-monolayer model exhibits substantial structural reorganization and produces a broad, dominant phonon sideband that is inconsistent with experiment. Adding an adjacent layer, either MoS$_2$ or hBN, substantially suppresses the phonon sideband, with only a minor dependence on the defect position in bilayer MoS$_2$. In particular, the MoS$_2$/hBN model yields a weak phonon sideband and closely reproduces the experimental photoluminescence lineshape. Our results thus provide the first theoretical agreement of CH$_\mathrm{S}^{-}$ emission and further reveal the role of adjacent layers in determining the electronic, vibronic, and optical properties of the quantum emitters in two-dimensional materials.

Quantum Physics (quant-ph); Materials Science (cond-mat.mtrl-sci)

arXiv:2610.12283 [quant-ph]

(or arXiv:2610.12283v1 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2610.12283 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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