Coherent dynamics of multi-spin V $${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ B − center in hexagonal boron nitride

Hexagonal boron nitride (hBN) has recently been demonstrated to contain optically polarized and detected electron spins that can be utilized for implementing qubits and quantum sensors in nanolayered-devices. Understanding the coherent dynamics of microwave driven spins in hBN is of crucial importance for advancing these emerging new technologies. Here, we demonstrate and study the Rabi oscillation and related phenomena of a negatively charged boron vacancy (V $${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ B − ) spin ensemble in hBN. We report on different dynamics of the V $${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ B − spins at weak and strong magnetic fields. In the former case the defect behaves like a single electron spin system, while in the latter case it behaves like a multi-spin system exhibiting multiple-frequency dynamical oscillation as beat in the Ramsey fringes. We also carry out theoretical simulations for the spin dynamics of V $${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ B − and reveal that the nuclear spins can be driven via the strong electron nuclear coupling existing in V $${}_{{{{{{{{\rm{B}}}}}}}}}^{-}$$ B − center, which can be modulated by the magnetic field and microwave field.