We report on the spatial and temporal coherence of interlayer exciton ensembles as photoexcited in MoSe2/WSe2 heterostructures and characterized by point-inversion Michelson-Morley interferometry. Below 10 K, the measured spatial coherence length of the interlayer excitons reaches values equivalent to the lateral expansion of the exciton ensembles. In this regime, the light emission of the excitons turns out to be homogeneously broadened in energy with a high temporal coherence. At higher temperatures, both the spatial and temporal coherence lengths decrease, most likely because of thermal processes. The presented findings point towards a spatially extended, coherent many-body state of interlayer excitons at low temperature.
2D materials offer a wide range of perspectives for hosting highly localized 0D states, e.g. vacancy defects, that offer great potential for integrated quantum photonic applications. Here, we create individual defects that act as our single-photon emitters by highly local He-ion irradiation in a monolayer MoS2 van der Waals heterostructure. The defects show anti-bunched light emission at a characteristic energy of ~ 1.75 eV. The emission is highly homogeneous and background free due to the hBN encapsulation with a creation yield of > 70%. Spectroscopic investigation of individual single-photon emitters reveals a strongly asymmetric line shape resembling interaction with acoustic phonons in excellent agreement with an independent boson model. Moreover, emitters are spatially integrated and electrically controlled in field-switchable van der Waals devices. Our work firmly establishes 2D materials as a highly scalable material platform for integrated quantum photonics.
Monolayers of semiconducting transition metal dichalcogenides excel due to their strong exciton dominated light matter interaction. We focus on monolayer MoS2 field effect structures and demonstrate that the degree of valley polarization that typically vanishes at elevated temperature can be restored even at room temperature by increasing the electron density. The recovering of the valley polarization via doping is linked to the suppression of the Fröhlich exciton LO-phonon interaction that mediates a uniaxial long-range oscillating electric field braking the three-fold rotational symmetry. Our results provide a promising strategy to increase the degree of valley polarization towards room temperature valleytronic applications.
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