Intersystem crossing and exciton-defect coupling of spin defects in hexagonal boron nitride

Despite the recognition of two-dimensional (2D) systems as emerging and scalable host materials of single-photon emitters or spin qubits, the uncontrolled, and undetermined chemical nature of these quantum defects has been a roadblock to further development. Leveraging the design of extrinsic defects can circumvent these persistent issues and provide an ultimate solution. Here, we established a complete theoretical framework to accurately and systematically design quantum defects in wide-bandgap 2D systems. With this approach, essential static and dynamical properties are equally considered for spin qubit discovery. In particular, many-body interactions such as defect-exciton couplings are vital for describing excited state properties of defects in ultrathin 2D systems. Meanwhile, nonradiative processes such as phonon-assisted decay and intersystem crossing rates require careful evaluation, which competes together with radiative processes. From a thorough screening of defects based on first-principles calculations, we identify promising single-photon emitters such as Si-VV and spin qubits such as Ti-VV and Mo-VV in hexagonal boron nitride. This work provided a complete first-principles theoretical framework for defect design in 2D materials.

Automated summary

This study established a complete theoretical framework for accurately and systematically designing quantum defects in wide-bandgap 2D systems, focusing on essential static and dynamic properties for spin qubit discovery. Through thorough screening of defects based on first-principles calculations, promising single-photon emitters and spin qubits were identified in hexagonal boron nitride.