Proximity Induced Chiral Quantum Light Generation in Strain-Engineered WSe2/NiPS3 Heterostructures*

An ability to control the polarization of the single photons generated by the quantum light emitters holds the key to the realization of non-reciprocal single-photon devices and complex quantum networks. To date, such control is usually achieved via coupling of the quantum emitters to the complex photonic/meta-structures, injection of spin-polarized carriers/excitons, or application of high magnetic fields.   “Proximity effects” – the class of phenomena by which an atomically-thin material borrows properties of an adjacent material (such as magnetism) via quantum mechanical interactions – has recently been explored to achieve this highly desired polarization control.  By coupling transition metal dichalcogenides with various bulk and 2D magnetic materials, exciting effects such as strong enhancement of valley Zeeman splitting and spin-dependent charge transfer have been demonstrated.  However, chiral light emission without spin-polarized carrier/exciton injection at zero magnetic field remains elusive to date.  We recently demonstrate that chiral quantum light sources with a high degree of circular polarization (>0.9) and 80% single-photon purity can be realized by strain-engineering the WSe₂/NiPS_3­ heterostructure with nanoscale indentations.¹  Through state of art scanning diamond NV microscopy experiments and temperature-dependent magneto-photoluminescence studies, we show that the chiral quantum light emission arises from magnetic proximity interactions between localized excitons in the WSe₂ monolayer and out-of-plane magnetization of AFM defects in NiPS₃, both of which are co-localized by the strain field arising from the nanoscale indentations. Interestingly, a similar chiral localized excitonic emission is also observed in our more recent experiment performed on WSe₂/MnPS₃ and WSe₂/FePS₃ heterostructure with nano-indents.