Computational search for the single-photon emitters among local defects in two-dimensional SnS­₂

The single photon emitters (SPE) in the near-infrared (NIR) range are important elements of the quantum communication technology. With a goal to reveal efficient NIR SPEs and based on educated guess, we preselected for consideration substitutional-doping defects in SnS₂. The defects were Y_X, where X = Sn or S, and Y = C, Si, Ge, N, P, and As (Y represents the dopant and X the substituted element). To evaluate the stability of the defects, we calculated their formation energy and phonon spectrum. For the stable defects, we applied the linear response GW and the Bethe-Salpeter equation (BSE) methods to obtain electronic structure and optical excitation spectra. We found that the Si_S, P_S-, and N_S- defects have sharp excitation peaks in NIR region. Analysis of the GW eigenstates contributing to the BSE eigenstates in question brings us to the conclusion that the optical emission associated with these excitations will have narrow zero-phonon lines with negligible phonon side bands.