Triplet ground state and optical excitations of local defects in cubic BN.

Boron nitride (BN) allotropes have been under intense scrutiny in the past decade as they may be suitable hosts for local defects that may function as spin qubits for quantum computers and thus serve as an alternative to the NV<span style="font-size:10.8333px">- defect hosted in diamond. In particular, the defect consisting of a B-vacancy and a neighboring O substitutional dopant in cubic BN (V_BO_N) has been reported to display a triplet ground state [1]. Our Density Functional Theory and GW calculations confirm the spin ground state of the V_BO_N but, importantly, our Bethe-Salpeter calculations indicate that V_BO_N has sharp optical excitations at 1.6 and 1.9 eV that suggest it could be a promising spin qubit [2]. Other substitutional dopants among the chalcogens, however, display a very different behavior as they have a singlet ground state and optical excitations at energies in the long-wave UV range (UVA) of modest transition probability.

[1] Bian et al. Appl. Phys. Lett. 114, 102105 (2019)