Excited-state spin-resonance spectroscopy of V_B^- defects in hexagonal boron nitride

Recently discovered spin-active boron vacancy (V_B^-) defect centers in hexagonal boron nitride (hBN) have high contrast optically-detected magnetic resonance (ODMR) at room temperature, with a spin-triplet ground-state that shows promise as a quantum sensor. In this talk, we present results using magnetic field-dependent spectroscopy to probe and manipulate spin within the orbital excited-state of V_B^- defects in hBN. Our experiments determine the excited-state spin Hamiltonian, including the temperature-dependent zero-field splitting parameters and the Landé g-factor. We confirm that the resonance is associated with spin rotation in the excited-state by carrying out pulsed ODMR measurements, and we observe Zeeman-mediated level anti-crossings in both the orbital ground- and excited-states. Our observation of a single excited-state spin resonance from 10 K to 300 K is consistent with a single accessible orbital state spin-triplet, which has consequences for understanding the symmetry of this point defect. Additionally, the excited-state ODMR has strong temperature dependence of both contrast and transverse anisotropy splitting, enabling promising new avenues for quantum sensing.