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

TL;DR

This study explores the spectral and spin properties of a mechanically isolated quantum emitter in hBN, revealing distinct spectral diffusion behaviors and spin-dependent dynamics crucial for quantum applications.

Contribution

It provides new insights into the spectral diffusion mechanisms and spin-related behaviors of isolated hBN quantum emitters, advancing understanding of their quantum coherence.

Findings

Bright resonant fluorescence with >10 Mc/s saturation rate

Two closely spaced zero-phonon-line transitions with different spectral diffusion dynamics

Spin-dependent population dynamics observed in metastable states

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.