Negatively charged boron vacancy center in diamond

Abstract

Impurity-vacancy complexes in diamond are an attractive family of spin defects since NV-, SiV-, GeV-, and SnV- have emerged as promising platforms for quantum applications. Although boron is most easily incorporated into diamond, a boron-vacancy complex in the negative charge state (BV-) has eluded experimental observation. This center was theoretically predicted as another promising spin qubit. In this work, we experimentally observed an electron paramagnetic resonance (EPR) spectrum identified as BV- in synthetic diamonds via a Fermi-level tuning. Fingerprints of BV- such as the spin multiplicity of S=1, C3v symmetry, and the zero-field splitting (D=2913 MHz), in addition to B10 and B11 hyperfine (HF) interactions, have been confirmed. Moreover, optically pumped spin polarization has been observed with 3.0-3.6 eV excitation. However, unlike the NV- center, the photoluminescence as well as optically detected magnetic resonance from BV- have not been confirmed even at low temperatures. We speculate that the Jahn-Teller instability in the triplet excited states of the NV- and BV- centers results in different optical properties.