T–X phase diagram of salicylic acid–anthranilic acid with three crystalline solid solution phases and a co-crystal, resulting in variable enantiotropic transition temperature and a polymorphic co-existence domain.

Spin defects in hexagonal boron nitride, and specifically the negatively charged boron vacancy (VB‐) centers, are emerging candidates for quantum sensing. However, the VB‐ defects suffer from low quantum efficiency and, as a result, exhibit weak photoluminescence. In this work, a scalable approach is demonstrated to dramatically enhance the VB‐ emission by coupling to a plasmonic gap cavity. The plasmonic cavity is composed of a flat gold surface and a silver cube, with few‐layer hBN flakes positioned in between. Employing these plasmonic cavities, two orders of magnitude are extracted in photoluminescence enhancement associated with a corresponding twofold enhancement in optically detected magnetic resonance contrast. The work will be pivotal to progress in quantum sensing employing 2D materials, and in realization of nanophotonic devices with spin defects in hexagonal boron nitride.

The binary T-X phase diagram of salicylic acid and benzoic acid have been experimentally determined from 25°C to melting. It is found to be dominated by two crystalline solid solutions...

Light carries both spin angular momentum (SAM) and orbital angular momentum (OAM), which can be used as potential degrees of freedom for quantum information processing. Quantum emitters are ideal candidates towards on-chip control and manipulation of the full SAM–OAM state space. Here, we show coupling of a spin-polarized quantum emitter in a monolayer W S e 2 with the whispering gallery mode of a S i 3 N 4 ring resonator. The cavity mode carries a transverse SAM of σ = ± 1 in the evanescent regions, with the sign depending on the orbital power flow direction of the light. By tailoring the cavity–emitter interaction, we couple the intrinsic spin state of the quantum emitter to the SAM and propagation direction of the cavity mode, which leads to spin–orbit locking and subsequent chiral single-photon emission. Furthermore, by engineering how light is scattered from the WGM, we create a high-order Bessel beam which opens up the possibility to generate optical vortex carrying OAM states.