Triplet ground state and optical excitations of local defects in hexagonal BeS bilayer.

Triplet ground states for spin-qubit applications have remained elusive in defected 2D semiconductors so far. In this study, however, Density-Functional-Theory and GW calculations for 5 strategically tailored local defects in the hexagonal BeS bilayer indicate that 4 defects display a triplet ground state. Bethe-Salpeter calculations show that, although the optical excitations with exceptionally large oscillator strength occur at energies below 0.3 eV, these defects may have potential applicability as spin-qubits and single-photon emitters because they also display optical excitations of moderate intensity within the near-infrared spectrum. Finite-difference phonon calculations at the G-point for a 4x4x1 supercell indicate that all studied defects are dynamically stable.

Gong et al. Journal of Alloys and Compounds 781 (2019) 371-377