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arXiv · 2604.14998

Investigating Spectral Dynamics and Spin Signatures of a Mechanically Isolated Quantum Emitter in hBN

Sajedeh Shahbazi·Alexander Pachl·Kathrin Schwer·Patrick Maier·Alexander Kubanek
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Abstract

Mechanically isolated defect centers in hexagonal boron nitride are promising coherent quantum emitters, yet spectral instabilities persist, and their spin-related nature remains unclear. Here we investigate a single mechanically isolated quantum emitter in hBN integrated onto a coplanar waveguide. The emitter exhibits exceptionally bright resonant fluorescence with saturation count rates exceeding $10\,\mathrm{Mc/s}$. High-resolution spectroscopy reveals two closely spaced zero-phonon-line transitions originating from the same defect complex. Time-resolved spectroscopy shows that these transitions exhibit markedly different spectral diffusion dynamics, consistent with distinct donor-acceptor-pair-like recombination pathways with different sensitivities to local electrostatic fluctuations. Off-resonant blue illumination redistributes emission between the two transitions and increases the emission duty cycle without significantly modifying the dominant spectral diffusion rates at low temperature, indicating repumping from long-lived shelving states. Magnetic-field-dependent photoluminescence, optically detected magnetic resonance, and pump-probe measurements reveal millisecond-scale relaxation dynamics and magnetic-field-dependent fluorescence contrast, demonstrating spin-dependent population dynamics in the metastable shelving state. These results clarify how charge-driven spectral fluctuations and spin-dependent shelving jointly shape the optical cycling dynamics.

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Sajedeh Shahbazi, Alexander Pachl, Kathrin Schwer, Patrick Maier, Alexander Kubanek. 2026-04-16. Investigating Spectral Dynamics and Spin Signatures of a Mechanically Isolated Quantum Emitter in hBN. https://arxiv.org/abs/2604.14998

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