Hexagonal boron nitride (h-BN) is a van der Waals material which hosts visible quantum emitters at room temperature. These emitters can host optically addressable spins for use as qubits or quantum sensors. However, the electronic structure of quantum emitters in h-BN remains unknown, in particular the optical dynamics. Many solid-state quantum emitters, such as the nitrogen-vacancy center in diamond, exhibit direct, phonon-assisted absorption and emission between electronic ground and excited states. However, these systems can also exhibit more complicated optical dynamics where radiative emission occurs in a different manifold from the optical pumping. Here, we probe these dynamics by investigating the photon emission statistics and spectroscopy of quantum emitters in h-BN under different excitation wavelengths and pumping powers. For several quantum emitters (representative emitter: Fig. 1a, 1b), we observe that the anti-bunching rate, τ<sub>1</sub><sup>-1</sup>, saturates at high pumping power (Fig. 1c) to a value equal to the fluorescence lifetime (Fig. 1d). In addition, the excitation and emission remain polarized (Fig. 1e), and the spectrum is consistent with a single phonon-assisted transition (Fig. 1f). These observations point to an indirect emission model where the optical excitation transiently populates an additional excited state. We discuss candidate electronic structures that explain this behavior.

Probing the optical dynamics of quantum emitters in hexagonal boron nitride

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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