Hexagonal boron nitride (hBN) has emerged as a promising two-dimensional platform for quantum sensing, due to its optically addressable spin defects, such as the negatively charged boron vacancy (VB−). Despite hBN being transferrable to close proximity to samples, spectral overlap of spin transitions due to large hyperfine interactions has limited its magnetic sensitivity. Here, we demonstrate spin-selective excitation of VB− spin defects in hBN driven by circularly polarized microwave. Using a cross-shaped microwave resonance waveguide, we superimpose two orthogonally linearly polarized microwave shifted in phase from a RFSoC FPGA to generate circularly polarized microwaves. This enables selective spin ∣0⟩→∣−1⟩ or ∣0⟩→∣1⟩ excitation of VB− defects, as confirmed by optically detected magnetic resonance experimentally and supported computationally. We also investigate the influence of magnetic field on spin-state selectivity. Our technique enhances the potential of hBN platform for quantum sensing through better spin state control and magnetic sensitivity particularly at low fields.
@article{arxiv.2506.04448,
title = {Spin-State Selective Excitation in Spin Defects of Hexagonal Boron Nitride},
author = {Mohammad Abdullah Sadi and Luca Basso and David A Fehr and Xingyu Gao and Sumukh Vaidya and Emmeline G Riendeau and Gajadhar Joshi and Tongcang Li and Michael E Flatté and Andrew M Mounce and Yong P Chen},
journal= {arXiv preprint arXiv:2506.04448},
year = {2025}
}