Optically Active Spin Defects in Few-Layer Thick Hexagonal Boron Nitride
Alrik Durand, T. Clua-Provost, Florentin Fabre, Pawan Kumar, Jiahan Li, James H. Edgar, Péter Udvarhelyi, Ádám Gali, X. Marie, Cédric Robert, Jean‐Michel Gérard, Bernard Gil, Guillaume Cassabois, V. Jacques
Abstract
Optically active spin defects in hexagonal boron nitride (hBN) are promising quantum systems for the design of two-dimensional quantum sensing units offering optimal proximity to the sample being probed. In this Letter, we first demonstrate that the electron spin resonance frequencies of boron vacancy centers (${V}_{\mathrm{B}}^{\ensuremath{-}}$) can be detected optically in the limit of few-atomic-layer thick hBN flakes despite the nanoscale proximity of the crystal surface that often leads to a degradation of the stability of solid-state spin defects. We then analyze the variations of the electronic spin properties of ${V}_{\mathrm{B}}^{\ensuremath{-}}$ centers with the hBN thickness with a focus on (i) the zero-field splitting parameters, (ii) the optically induced spin polarization rate and (iii) the longitudinal spin relaxation time. This Letter provides important insights into the properties of ${V}_{\mathrm{B}}^{\ensuremath{-}}$ centers embedded in ultrathin hBN flakes, which are valuable for future developments of foil-based quantum sensing technologies.