Photodynamics and Temperature Dependence of Single Spin Defects in Hexagonal Boron Nitride

Quantum emitters in hexagonal boron nitride (hBN) that exhibit optically detected magnetic resonance (ODMR) signatures have recently garnered significant attention as an emerging solid-state platform for quantum technologies. However, the underlying spin dynamics and the mechanisms determining the spin-dependent fluorescence in these defects are still poorly understood. In this work, we perform detailed photodynamical studies of the spin complexes in hBN. In particular, we show that spin transitions are located within the metastable manifold, which can be explained by the rate model, populating in a cascading manner. In addition, we perform temperature-dependent measurements on these defects and show that the spin-lattice relaxation and coherence times increase as the temperature decreases. Furthermore, we find that the ODMR frequencies of the S = 1 transition show only a marginal frequency shift as a function of temperature, which makes them a robust sensor at cryogenic temperatures. These insights are crucial for further understanding of the spin dynamics of quantum emitters in hBN and their practical implementation in quantum sensing.