First-Principles Predictions of Out-of-Plane Group IV and V Dimers as High-Symmetry, High-Spin Defects in Hexagonal Boron Nitride

Abstract

Hexagonal boron nitride (h-BN) has been recently found to host a variety of quantum point defects, which are promising candidates as single-photon sources for solid-state quantum nanophotonic applications. Most recently, optically addressable spin qubits in h-BN have been the focus of intensive research due to their unique potential in quantum computation, communication, and sensing. However, the number of highsymmetry, high-spin defects that are desirable for developing spin qubits in h-BN is highly limited. Here, we combine density functional theory (DFT) and quantum embedding theories to show that out-of-plane X N Y i dimer defects (X, Y = C, N, P, and Si) form a new class of stable C 3v spin-triplet defects in h-BN. We find that the dimer defects have a robust 3 A 2 ground state and 3 E excited state, both of which are isolated from the h-BN bulk states. We show that 1 E and 1 A shelving states exist and they are positioned between the 3 E and 3 A 2 states for all the dimer defects considered in this study. To support future experimental identification of the X N Y i dimer defects, we provide extensive characterization of the defects in terms of their spin and optical properties. We predict that the zero-phonon line of the spin-triplet X N Y i defects lies in the visible range (800 nm to 500 nm). We compute the zero-field splitting of the dimers' spin to range from 1.79 GHz (Si N P i 0 ) to 29.5 GHz (C N N i 0 ). Our results broaden the scope of high-spin defect candidates that would be useful for the development of spin-based solid-state quantum technologies in twodimensional hexagonal boron nitride.

Spin-active defects in hexagonal boron nitride

“…In addition to the above mentioned works, there are many efforts to find high-spin defects which are key quantities to develop nanoscale sensors [167,168]. Bhang et al [167] reported that out-of-plane X N Y i dimer defects (X, Y = C, N, P, and Si) form a new class of stable C 3v spin-triplet (S = 1) defects in hBN. Smart et al [168] reported that Ti VV and Mo VV defects in hBN have a neutral triplet GS (S = 1).…”

Coherent Quantum Emitters in Hexagonal Boron Nitride

“…Recently, simulations for out‐of‐plane defects, in particular group IV and V dimers, have been performed and discussed in the context of high‐symmetry, high‐spin defect centers. [ 116 ] Applying similar modeling to the orbital structure of mechanically isolated defect centers could be a promising path forward to investigate the underlying decoupling mechanism. The apparent universality of the mechanical isolation mechanism, resulting in isolated emitters with a large range of ZPL transition wavelengths, enables applications in a broad range.…”

First-principles theory of the nitrogen interstitial in hBN: a plausible model for the blue emitter

“…Furthermore, these defects were also discussed in several recent theoretical works. [21][22][23][24][25] On the other hand, no comprehensive theoretical studies have been carried out for these candidates.…”