Enhanced Emission from Boron-Vacancy Center in Rhombohedral Boron Nitride

Abstract

Various stacking combinations of the two-dimensional (2D) boron nitride (BN) honeycomb lattice can significantly modify the properties of the resulting 2D BN crystal. Here, we demonstrate through first-principles calculations that the brightness of the negatively charged boron-vacancy center (V$_\text{B}^{-}$) is enhanced by at least one order of magnitude in rhombohedral BN (rBN) compared to hexagonal BN (hBN), while the spin properties remain either comparable or even improved. This enhancement arises from the reduced symmetry of the crystal field in rBN. Our results suggest that room-temperature single-spin coherent control of V$_\text{B}^{-}$ is feasible in rBN, enabling its application as a single-spin quantum sensor in this 2D host. These findings demonstrate that engineered stacking of BN layers provides a powerful means to tailor the properties of embedded quantum defects.

Figures (6)

• Figure 1: Electronic structure of V$_\text{B}^{-}$ in rBN. (a) Geometry of V$_\text{B}^{-}$ with the calculated spin density. (b) Kohn-Sham electronic structure from HSE DFT calculation. (c) Many-body electronic structure from GW+BSE where the composition of the exciton wavefunction is indicated beside the symmetry label of the muliplet excited states. The radiative lifetimes ($\tau_\text{rad}$) are given as derived from the BSE spectrum. (d) Vertical optical excitation spectrum with the first excitonic peak at 1.72 eV. The red (blue) color represents the photon polarization perpendicular (parallel) to the C$_3$ rotation axis. The optical transition dipole moments are also given in Debye unit. (e) Visualization of the Kohn-Sham orbitals. Note that the planar symmetry is broken.
• Figure 1: Partial Huang-Rhys factors individually distributed into totally symmetric $A_1$ and Jahn-Teller active $E$ modes at 0 K temperature.
• Figure 2: Photoluminescence spectrum of V$_\text{B}^{-}$ in rBN at 4 K and 300 K from HSE DFT calculations. Zero-phonon-line (ZPL) peak appears and structured phonon sideband at low temperature. We note that the computed ZPL peak could have an inaccuracy of about 0.1 eV so the computed spectrum may be shifted when directly compared to experimental data.
• Figure 2: Calculated spin density. (a) Ground state. (b) Excited state. The vacant boron site located in the middle layer of rBN is depicted as a semitransparent green ball.
• Figure 3: Spin properties of V$_\text{B}^{-}$ in rBN. (a) cw-ODMR spectra at 9 mT (0 mT inset) magnetic fields.