Fig. 1: Spin-active V\({}_{{{{{{{{\rm{B}}}}}}}}}^{-}\) defects in hBN.
a Schematic of the device used to probe spin transitions of V\({}_{{{{{{{{\rm{B}}}}}}}}}^{-}\) defects in hBN. hBN flakes are transferred onto a gold-film coplanar waveguide (CPW) and the generated microwave field BMW induces rotations of the defect spin state which is read out via PL. b Schematic of the experimental setup. AOM acousto-optic modulator, BS beam splitter, FSM fast-steering mirror, MO microscope objective, LP long-pass filter, SP short-pass filter, FM flip mirror, APD avalanche photodiode. c Energy level diagram of the defect orbital states and their spin sublevels, which are split by Des and Dgs in the ES and GS, respectively. A non-radiative ISC to a singlet state is preferred from the \(\left|\pm 1\right\rangle\) spin sublevels of the ES. d Zero-field ODMR spectrum at T = 10 K, excited with laser power PL ≈ 3 mW and microwave power PMW ≈ 160 mW, showing distinct resonance dips from spin transitions in the ES (red) and GS (blue) at their respective splitting frequencies. The error bar represents shot noise from photon counting.
