Spin-State-Selective Excitation in Spin Defects of Hexagonal Boron Nitride.

Sadi, Mohammad Abdullah; Basso, Luca; Fehr, David A; Gao, Xingyu; Vaidya, Sumukh; Riendeau, Emmeline G; Joshi, Gajadhar; Li, Tongcang et al. · Nano Lett · 2025

basic_science · Level V

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Abstract

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 (V<sub>B</sub><sup>-</sup>). Spectral overlap of spin transitions due to large hyperfine interactions has limited its magnetic sensitivity. Here, we demonstrate spin-selective excitation of V<sub>B</sub><sup>-</sup> spin defects in hBN driven by a circularly polarized microwave. Using a cross-shaped microwave resonance waveguide, we superimpose two orthogonally linearly polarized microwaves shifted in phase from an FPGA to generate circularly polarized microwaves. This enables selective spin |0⟩ → |-1⟩ or |0⟩ → |1⟩ excitation of V<sub>B</sub><sup>-</sup> defects, as confirmed by optically detected magnetic resonance experimentally and supported computationally. We also investigate the influence of the magnetic field on spin-state selectivity. Our technique enhances the hBN platform for quantum sensing through better spin state control and magnetic sensitivity at low and zero fields.