Optical And Spin Dynamics Of Quantum Emitters In Hexagonal Boron Nitride At Room Temperature

Hexagonal boron nitride (h-BN) is a van der Waals material that hosts defect-based quantum emitters (QEs) at room temperature, providing an unparalleled platform for realizing devices for quantum technologies and studying light-matter interactions. Recent observations suggest the existence of multiple distinct defect structures responsible for QEs. Theoretical proposals suggest vacancies, substitutional atoms, and their complexes as likely defect candidates. However, experimental identification of the QEs’ electronic structure is lacking, and key details of the QEs’ charge and spin properties remain unknown. This thesis focuses on understanding the optical and spin dynamics of QEs in h-BN at room temperature. Starting with the motivation for studying quantum systems and QEs in Chapter 1, this thesis introduces QEs in h-BN in Chapter 2 and discusses its current understanding in Chapter 3. Chapter 4 discusses the materials and methods developed and utilized during the course of this thesis. Chapter 5 discusses the optical dynamics acquired using photoluminescence spectroscopy and photon emission correlation spectroscopy (PECS) and shows several QEs exhibit pure single-photon emission. It discusses the complex optical dynamics associated with excitation and relaxation through multiple electronic excited states - revealed by PECS and polarization-resolved excitation and emission. Following, it presents the optical dynamics simulations of electronic structure models that are consistent with the observations, and discusses the results in the context of ab initio theoretical calculations. Chapter 6 discusses magnetic-field-dependent PECS that can be used as a framework to probe the presence of single spins that are otherwise elusive. Following, it presents detection and confirmation of single spin using optically detected magnetic resonance. Finally, it discusses the spin dynamics and time-domain measurements acquired using optical and microwave pulse protocols crucial to developing methods to coherently control the QE’s spin. To conclude, Chapter 7 discusses the future directions that can help identify the chemical nature of QEs in h-BN and establish it as a scalable material platform for quantum technologies.