Intrinsic high-fidelity spin polarization of charged vacancies in hexagonal boron nitride

TL;DR

This study demonstrates near-unity spin polarization of charged boron vacancies in hexagonal boron nitride at room temperature, supported by measurements, modeling, and simulations that reveal hyperfine interactions and magnetic field effects.

Contribution

The paper introduces a semiclassical model predicting high spin polarization in V_B^- defects, including nuclear spin effects, validated by experiments and numerical simulations.

Findings

Near-unity spin polarization predicted and observed.

Hyperfine interactions influence nuclear spin polarization.

Magnetic field modulates polarization features.

Abstract

The negatively charged boron vacancy ($\mathrm{V}_{\mathrm{B}}^-$) in hexagonal boron nitride (hBN) has garnered significant attention among defects in two-dimensional materials. This owes, in part, to its deterministic generation, well-characterized atomic structure, and optical polarizability at room temperature. We investigate the latter through extensive measurements probing both the ground and excited state polarization dynamics. We develop a semiclassical model based on these measurements that predicts a near-unity degree of spin polarization, surpassing other solid-state spin defects under ambient conditions. Building upon our model, we include the presence of nuclear spin degrees of freedom adjacent to the $\mathrm{V}_{\mathrm{B}}^-$ and perform a comprehensive set of Lindbladian numerics to investigate the hyperfine-induced polarization of the nuclear spins. Our simulations predict a number of important features that emerge as a function of magnetic field which are borne out by experiment.