Cooperative Emission from Quantum Emitters in Hexagonal Boron Nitride Layers

Collective light emission from many-body quantum systems is a cornerstone of quantum optics, yet its implementation in solid-state platforms operating under ambient conditions remains highly challenging. Large-bandgap van der Waals materials such as hexagonal boron nitride (hBN) host stable room-temperature single-photon emitters with narrow linewidths across a broad spectral range. However, cooperative radiative effects in this system have not been previously explored. Here we demonstrate collective emission from quantum-emitter ensembles in hBN layers when the emitters are nearly indistinguishable and positioned within a sub-wavelength proximity. Using confocal microscopy and a Hanbury Brown-Twiss (HBT) configuration, we identify both isolated emitters and ensembles activated by localized electron-beam irradiation. Time-resolved photoluminescence measurements reveal a superlinear intensity enhancement and a pronounced acceleration of the radiative decay in tightly confined ensembles, with lifetimes approaching the temporal resolution of our experimental system (about 500 ps), compared to approximately 1.85 ns for single emitters or large, spatially extended ensembles. Complementary second-order photon-correlation measurements exhibit sub-Poissonian antidip consistent with emission from a few indistinguishable emitters. The simultaneous observation of lifetime shortening and enhanced emission provides direct evidence of cooperative emission at room temperature, achieved without optical cavities or cryogenic cooling. These results establish optically active defect ensembles in hBN as a scalable solid-state platform for engineered collective quantum optics in two-dimensional materials, opening avenues toward ultrabright superradiant light sources and nonclassical photonic states for quantum technologies.