Computational Design of Single Photon Emitters and Spin Qubits in defected bulk and bilayer BeS

Local defects in wide bandgap semiconductors are of great interests due to potential properties that could make them viable for spin-qubit and single-photon emitter (SPE) functionalities, which are at the core of quantum information technologies. In this work, we have designed SPEs and spin-qubits, where BeS semiconductor - both its bulk and bilayer form – serves as a host for the defects under consideration. Using the existing knowledge within the field, we selected a number of defects which combine Be vacancies with S substitutions. The stability of the defects was evaluated by calculating formation energies and phonon spectra within the density-functional theory (DFT). Then, the linear-response GW method and Bethe-Salpeter equation (BSE) technique were used to obtain the electronic structure and optical properties of the defects in question. Analysis of the obtained results suggest several defects have formidable properties for single photon emission, while others are found to be suitable for an optical polarization cycle, essential for optically controlled spin-qubit.