Optically-Addressable Spins in Hexagonal Boron Nitride: Creation, Identification, and Characterization

Optically-addressable spins associated with localized defects in wide-bandgap semiconductors are the basis for rapidly expanding quantum technologies in nanoscale sensing and quantum information processing. Whereas most research has focused on three-dimensional host materials such as diamond, the van der Waals material hexagonal boron nitride (hBN) has emerged as a robust host for bright, stable, room-temperature quantum emitters (QEs). However, many questions persist regarding the chemical and electronic structure of the defects responsible for emission as well as the potential role of spin-related effects. Significantly complicating the identification are the heterogeneity of optical characteristics observed for these QEs.

In this talk, I will describe the optical and magnetic properties of QEs in hBN characterized using confocal fluorescence microscopy on suspended hBN films. Qualitative similarities in excitation and emission polarization, spectral shape, and emission statistics are evident among QEs in hBN, even for large variations in emission energy [1]. Significantly, a small percentage of observed QEs exhibit strongly anisotropic photoluminescence modulation in response to an applied magnetic field in ambient conditions [2]. The magnetic-field-induced modulation is consistent with an electronic model featuring a spin-dependent inter-system crossing between triplet and singlet manifolds, suggesting that these defects host optically addressable spin states. This discovery enables the realization of spin-based quantum technologies with van der Waals heterostructures.

[1] Exarhos et al., ACS Nano 11, 3328 (2017).
[2] Exarhos et al., arXiv:1804.09061 [quant-ph] (2018). Nature Communications (accepted).

In collaboration with D. A. Hopper, R. N. Patel, R. R. Grote, A. Breitweiser, A. Alkauskas, M. W. Doherty, and L. C. Bassett.