Optical Detection of Sliding Ferroelectric Switching in hBN with a WSe Monolayer.

When two BN layers are stacked in parallel in an AB or BA arrangement, a spontaneous out-of-plane electric polarization arises due to charge transfer in the out-of-plane B-N bonds. The ferroelectric switching from AB to BA (or BA to AB) can be achieved with a relatively small out-of-plane electric field through the in-plane sliding of one atomic layer over the other. However, the optical detection of such ferroelectric switching in hBN has not yet been demonstrated.

Impact of Thickness-Dependent Nanophotonic Effects on the Optical Response of Color Centers in Hexagonal Boron Nitride.

Among a broad diversity of color centers hosted in layered van der Waals materials, the negatively charged boron vacancy (V) center in hexagonal boron nitride (hBN) is garnering considerable attention for the development of quantum sensing units on a two-dimensional platform. In this work, we investigate how the optical response of an ensemble of V centers evolves with the hBN thickness in a range of a few to hundreds of nanometers. We show that the photoluminescence intensity features a nontrivial evolution with thickness, which is quantitatively reproduced by numerical calculations taking into account thickness-dependent variations of the absorption, radiative lifetime, and radiation pattern of V centers.

Isotopic Control of the Boron-Vacancy Spin Defect in Hexagonal Boron Nitride.

We report on electron spin resonance (ESR) spectroscopy of boron-vacancy (V_{B}^{-}) centers hosted in isotopically engineered hexagonal boron nitride (hBN) crystals. We first show that isotopic purification of hBN with ^{15}N yields a simplified and well-resolved hyperfine structure of V_{B}^{-} centers, while purification with ^{10}B leads to narrower ESR linewidths. These results establish isotopically purified h^{10}B^{15}N crystals as the optimal host material for future use of V_{B}^{-} spin defects in quantum technologies.